TY - JOUR
A1 - Brirmi, M
A1 - Chabbah, T.
A1 - Chatti, S.
A1 - Schiets, F.
A1 - Casabianca, H.
A1 - Marestin, C.
A1 - Mercier, R.
A1 - Weidner, Steffen
A1 - Errachid, A.
A1 - Jaffrezic-Renault, N.
A1 - Ben Romdhane, H.
T1 - Effect of the pendent groups on biobased polymers, obtained from click chemistry suitable, for the adsorption of organic pollutants from water
N2 - In this work, four triazole-based poly(ether-pyridine)s polymers were synthesized and used as an adsorbent for the removal of phenolic compounds from aqueous solutions. For this purpose, new fluoromonomers containing 1,2,3-triazole units were prepared by the Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction and then used for the elaboration of novel poly(ether-pyridine-triazole)s (PEPTs) by direct polyconden-sation with isosorbide and bisphenol A. Chemical structure of fluorinated pyridinicmonomers as well as resulting polymers was confirmed by 1H and 19F NMR spectroscopic methods. The thermal behavior of the obtained PEPTs was characterized using differential scanning calorimetry and thermogravimetric analysis. Results of sorption showed that polymers can be effectively used as a sorbent for the removal of polarorganic pollutants. The isosorbide-based poly(ether-pyridine-triazole) which contains hydrophilic hydroxyl groups as pendants chains (P4) exhibited the highest sorption efficiencies (78%–100% after 1 h). In order to explain the results an adsorption mech-anism mainly based on π–π interactions and hydrogen bonding with the pendent groups is proposed.
KW - Adsorption
KW - Biobased polymers
KW - Cycloaddition
KW - Pentafluoropyridine
KW - Phenolic compounds
PY - 2022
DO - https://doi.org/10.1002/pat.5809
SN - 1042-7147
SP - 1
EP - 21
PB - Wiley online library
AN - OPUS4-55389
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Jlalia, I.
A1 - Gomri, M.
A1 - Chabbah, T.
A1 - Chatti, S.
A1 - Weidner, Steffen
A1 - Abderrazak, H.
A1 - Marestin, C.
A1 - Mercier, R.
A1 - Ben Halima, H.
A1 - Lakard, B.
A1 - Jaffrezic Renault, N.
T1 - Design of Fluorinated Poly(Ether-Pyridine) Films for Impedimetric Detection of Heavy Metal Ions
N2 - A series of fluorinated poly(ether-pyridine)s were synthesized via polycondensation of bis-perfluoropyridine with either bisphe-nol A (BPA) or isosorbide, a bio-sourced diol. The polymers were characterized using 1 H and 19 F NMR spectroscopy, and their molecular weights were determined using GPC. Thermal properties were assessed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The presence of isosorbide in polymer P2 increases the glass transition temperature and results in a lower molecular weight and a higher hydrophilicity. On the other hand, polymer P3, based on BPA, shows the best thermal stability, the highest molecular weight, and the most pronounced hydrophobic character. Electrochemical impedance spectroscopy (EIS) was used to evaluate the modified gold electrodes for the selective detection of metal ions. Among the four target ions (Ni 2+, Cd 2+, Pb2+, and Hg 2+), defined by the European Water Framework Directive, Pb2+ was selectively detected on the hydrophilic polymer P2, while Cd 2+ was selectively detected on the hydrophobic polymer P3. The achieved detection limits were 5 × 10−11 M, corresponding to 10 ng/L for Pb2+ and 5.6 ng/L for Cd 2+, respectively.
KW - Cadmium
KW - Electrochemical impedance spectroscopy
KW - Fluorinated polyether pyridines
KW - Isosorbide
KW - Lead
PY - 2025
DO - https://doi.org/10.1002/pat.70038
SN - 1099-1581
VL - 36
IS - 1
SP - 1
EP - 14
PB - John Wiley & Sons Ltd.
AN - OPUS4-62384
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Chabbah, T.
A1 - Chatti, S.
A1 - Zouaoui, F.
A1 - Jlalia, A.
A1 - Gaiji, H.
A1 - Abderrazak, H.
A1 - Casablanca, H.
A1 - Mercier, R.
A1 - Weidner, Steffen
A1 - Errachid, A.
A1 - Marestin, C.
A1 - Jaffrezic-Renault, N.
T1 - New poly(ether-phosphoramide)s sulfides based on green resources as sensitive films for the specific impedimetric detection of nickel ions
N2 - For the development of selective and sensitive chemical sensors, we have developed a new family of poly(etherphosphoramide) polymers. These polymers were obtained with satisfactory yields by nucleophilic aromatic polycondensation using isosorbide as green resources, and bisphenol A with two novel difluoro phosphinothioic amide monomers. Unprecedented, the thiophosphorylated aminoheterocycles monomers, functionalized with two heterocyclic amine, N-methylpiperazine and morpholine were successfully obtained by nucleophilic substitution reaction of P(S)–Cl compound. The resulting polymers were characterized by different analytical techniques (NMR, MALDI–ToF MS, GPC, DSC, and ATG). The resulting partially green polymers, having tertiary phosphine sulfide with P–N side chain functionalities along the main chain of polymers are the sensitive film at the surface of a gold electrode for the impedimetric detection of Cd, Ni, Pb and Hg. The bio-based poly(etherphosphoramide) functionalized with N-methylpiperazine modified sensor showed better analytical performance
than petrochemical based polymers for the detection of Ni2+. A detection limit of 50 pM was obtained which is very low compared to the previously published electrochemical sensors for nickel detection.
KW - Poly(ether-phosphoramide)s sulfides
KW - Green chemistry
KW - Polymer film
KW - MALDI TOF MS
PY - 2022
DO - https://doi.org/10.1016/j.talanta.2022.123550
VL - 247
IS - 123550
SP - 1
EP - 9
PB - Elsevier B.V.
AN - OPUS4-54980
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Chabbah, T.
A1 - Chatti, S.
A1 - Jaffrezic-Renault, N.
A1 - Weidner, Steffen
A1 - Marestin, C.
A1 - Mercier, R.
T1 - Impedimetric sensors based on diethylphosphonate-containingpoly(arylene ether nitrile)s films for the detection of lead ions
N2 - This article describes the elaboration and characterization of diethylphosphonate-containing polymers coated electrodes as sensors for the detection of heavy metalstraces, by electrochemical impedance spectroscopy. Diethylphosphonate groupswere chosen as heavy metals binding sites. Two different series of polymers bearingthese anchoring groups were synthesized. Whereas the diethylphosphonate groupsare directly incorporated in the aromatic macromolecular chain in some polymers, analiphatic spacer is removing the chelating site from the polymer backbone in others.The influence of the macromolecular structure on the sensing response was studied,especially for the detection of Pb2+,Ni2+,Cd2+and Hg2+. Polymer P6, including thehigher amount of diethylphosphonate groups removed from the polymer chain by ashort alkyl spacer gave the higher sensitivity of detection of lead ions, with a detec-tion limit of 50 pM
KW - Heavy metals
KW - Phosphonate esters
KW - Lead ions
KW - MALDI TOF MS
PY - 2023
DO - https://doi.org/10.1002/pat.6065
SN - 1042-7147
SP - 1
EP - 11
PB - John Wiley & Sons, Ltd
AN - OPUS4-57356
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Rösler, Alexander
A1 - Weidner, Steffen
A1 - Klamroth, Tillmann
A1 - Müller, Axel HE
A1 - Schlaad, Helmut
T1 - Kinetics of anionic polymerization of β‐myrcene in hydrocarbon solvents
N2 - AbstractThe kinetics of anionic polymerization of β‐myrcene initiated by sec‐butyllithium were examined in saturated and unsaturated hydrocarbon solvents, i.e. cyclohexane, cyclohexene, 4‐vinylcyclohexene and dl‐limonene. Polymerizations usually proceeded in a living manner, i.e. in the absence of termination and chain transfer reactions, in all solvents, to produce well‐defined polymyrcenes with high content (85%) of cis‐1,4 units. However, polymyrcenyllithium chains exhibited limited long‐term stability in 4‐vinylcyclohexene solution, most probably due to chain transfer to solvent. Reaction orders with respect to the concentration of active chains were found to be one‐quarter in cyclohexane increasing to one‐half in unsaturated solvents, indicating that the polymyrcenyllithium chains are present as tetrameric or dimeric associates, respectively. Apparent activation energies were found to be 81 kJ mol−1 in cyclohexane and 77 kJ mol−1 in dl‐limonene solution, which are close to the values obtained by quantum chemical calculations. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
KW - Myrcene
KW - Anionic polymerization
KW - MALDI TOF MS
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-649039
DO - https://doi.org/10.1002/pi.6772
SN - 0959-8103
SP - 1
EP - 8
PB - Wiley
AN - OPUS4-64903
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-ToF mass spectrometry for the characterization of biobased polymers suitable for depollution
N2 - In this work, bio-based polymers were synthesized and designed as polymers phases for adsorption of a variety of pollutants from aqueous solutions. The obtained adsorption results showed that the integration of bio-sourced synthons generate attractive hydrophilicity, and wettability of the resulting adsorbent phase. Such polymers phases enable stronger interactions with the organic and inorganic pollutants in water.
A wide variety of different bio-based polymers structures (e. g. poly(ethersulfones, poly(etherphosphines or poly(etherpyridines) with different functional groups were successfully designed in order to adapt chemical structure to different pollutants type and matrice nature.
In order to characterize and to determine the correlation between polymer structures and nature of interaction with pollutants, different analytical technics (NMR, GPC, ATG, DSC, Mass spectrometry) were successfully used. Amongst them, MALDI TOF mass spectrometry plays a superior role since this technique enables the simultaneous determination of the polymer structure, polymer end groups and molecular weight.
This work focusses on the characterization of synthesized polymers. The chemical structure of the repeating unit, the nature of the end groups, as well as the molecular weight, which are all important for the specific interactions of the polymer with the pollutants were clearly determined and suggestions to improve these interactions by changing the synthetic pathway could be given.
T2 - 12. Journees maghreb-europe. Matériaux et Applications aux Dispositifs et Capteurs
CY - Monastir, Tunisia
DA - 08.11.2022
KW - MALDI TOF MS
KW - Biobased polymers
KW - Depollution
PY - 2022
AN - OPUS4-56237
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Decker, Renate
A1 - Roessner, D.
A1 - Friedrich, Jörg Florian
T1 - Influence of Plasma Treatment on the Molar Mass of Poly(ethylene terephthalate) Investigated by Different Chromatographic and Spectroscopic Methods
N2 - The influence of different types of low and atmospheric pressure plasma on poly(ethylene terephthalate) (PET) has been studied in terms of changes in molar mass and molar mass distribution. Apart from a variation of plasma gases (oxygen, helium) different types of plasma (microwave, radio frequency, corona discharge) were used for the plasma surface modification. The changes in molar mass and types of functional end groups of lower molar mass products were investigated by means of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOFMS), whereas the high-molar mass fraction was analyzed by means of size-exclusion chromatography (SEC). The formation of crosslinked products during exposure to a helium plasma, which emits preponderately energy-rich and intense ultraviolet radiation, was proved by means of thermal field-flow fractionation (ThFFF). This method combined with a multiangle laser light scattering (MALLS) detector allows detection of weakly crosslinked polymers and microgels. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1639-1648, 1998
KW - Poly(ethylene terephthalate)
KW - PET
KW - Plasma
PY - 1998
UR - http://www3.interscience.wiley.com/cgi-bin/abstract/36482/ABSTRACT
DO - https://doi.org/10.1002/(SICI)1099-0518(19980730)36:10<1639::AID-POLA17>3.0.CO;2-H
SN - 0360-6376
SN - 0887-624X
VL - 36
IS - 10
SP - 1639
EP - 1648
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-6989
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Czichocki, G.
A1 - Fiedler, H.
A1 - Haage, K.
A1 - Much, Helmut
A1 - Weidner, Steffen
T1 - Characterization of alkyl polyglycosides by both reversed-phase and normal-phase modes of high-performance liquid chromatography
N2 - Alkyl polyglycosides today represent the most important sugar surfactant. Nonionic sugar surfactants produced via different synthetic routes are mixtures of alkyl homologues, oligomers, anomers and isomers. Alkyl homologues and oligomers of alkyl mono- and diglucosides were separated by reversed-phase high-performance liquid chromatography (HPLC) with methanolwater as the mobile phase using a gradient elution. The gradient was optimized in respect to a simultaneous separation of alkyl glycosides according to their alkyl chain length and alkyl polyoxyethylene glucosides with regard to their length of the polyoxyethylene spacer. The separation of alkyl glycosides into ?- and ?-anomers was carried out by normal-phase HPLC with isooctaneethyl acetate (60:40, v/v)2-propanol in the gradient mode. Light scattering detection was used. Matrix-assisted laser desorption ionization time-of-flight mass spectra of alkyl glucosides and dodecyl glucosides with oxyethylene spacer groups are presented.
PY - 2002
DO - https://doi.org/10.1016/S0021-9673(01)01459-5
SN - 0021-9673
VL - 943
IS - 2
SP - 241
EP - 250
PB - Elsevier
CY - Amsterdam
AN - OPUS4-11099
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lauer, Franziska
A1 - Diehn, Sabrina
A1 - Seifert, Stephan
A1 - Kneipp, Janina
A1 - Sauerland, V.
A1 - Barahona, C.
A1 - Weidner, Steffen
T1 - Multivariate analysis of MALDI imaging mass spectrometry data of mixtures of single pollen grains
N2 - Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrixassisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from > 10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted.
Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry.
KW - MALDI Imaging MS
KW - Pollen grains
KW - Multivariate Statistics
KW - Hierarchical cluster analysis
KW - Principal component analysis
PY - 2018
DO - https://doi.org/10.1007/s13361-018-2036-5
SN - 1044-0305
SN - 1879-1123
VL - 29
IS - 11
SP - 2237
EP - 2247
PB - Springer
AN - OPUS4-45607
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sötebier, Carina
A1 - Bierkandt, Frank
A1 - Rades, Steffi
A1 - Jakubowski, Norbert
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Sample loss in asymmetric flow field-flow fractionation coupled to inductively coupled plasma-mass spectrometry of silver nanoparticles
N2 - In this work, sample losses of silver nanoparticles (Ag NPs) in asymmetrical flow field-flow fractionation (AF4) have been systematically investigated with the main focus on instrumental conditions like focusing and cross-flow parameters as well as sample concentration and buffer composition. Special attention was drawn to the AF4 membrane. For monitoring possible silver depositions on the membrane, imaging laser ablation coupled to inductively coupled plasma mass spectrometry (LA-ICP-MS) was used. Our results show that the sample residue on the membrane was below 0.6% of the total injected amount and therefore could be almost completely avoided at low sample concentrations and optimized conditions. By investigation of the AF4 flows using inductively coupled plasma mass spectrometry (ICP-MS), we found the recovery rate in the detector flow under optimized conditions to be nearly 90%, while the cross-flow, slot-outlet flow and purge flow showed negligible amounts of under 0.5%. The analysis of an aqueous ionic Ag standard solution resulted in recovery rates of over 6% and the ionic Ag content in the sample was found to be nearly 8%. Therefore, we were able to indicate the ionic Ag content as the most important source of sample loss in this study.
KW - Asymmetric flow filed-flow fractionation
KW - ICP-MS
KW - Nanoparticles
KW - Sample loss
KW - Quantification
PY - 2015
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-336171
DO - https://doi.org/10.1039/c5ja00297d
SN - 0267-9477
SN - 1364-5544
VL - 30
IS - 10
SP - 2214
EP - 2222
PB - Royal Society of Chemistry
CY - London
AN - OPUS4-33617
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans
A1 - Weidner, Steffen
A1 - Scheliga, Felix
T1 - Ring-Expansion Polymerization (REP) of L-lactide with cyclic Tin(II) Bisphenoxides
N2 - Five new cyclic catalysts were prepared by a new synthetic method from tin(II)-2-ethyhexanoate and silylated catechols, silylated 2,2´dihydroxybiphenyl or silylated 1,1´-bisnaphthol. These catalysts were compared with regard to their usefulness as catalysts for the ring expansion polymerization (REP) of L-lactide in bulk at 160 °C, and with two different tin(IV) derivatives of 1,1´binaphthol. Best results were obtained using seven-membered cyclic tin(II)bisphenoxides, which yielded colorless cyclic poly(l-lactide)s free of racemization with weight average molecular weights (Mw) up to 305 000 g mol-1. Furthermore, these catalysts were active even at a lactide/catalyst ratio of 20 000/1. Our new results were superior to those obtained from all other previously published catalysts yielding cyclic poly(L-lactide). The seven-membered cycles also proved to be more active than tin(II) 2-ethylhexanoate with and without the addition of alcohol.
KW - Lactide
KW - Cyclization
KW - Ring-expansion polymerization
KW - Tin(II)octanoate
KW - MALDI-TOF MS
PY - 2019
DO - https://doi.org/10.1016/j.eurpolymj.2019.04.024
SN - 0014-3057
SN - 1873-1945
VL - 116
SP - 256
EP - 264
PB - Elsevier Ltd.
AN - OPUS4-47794
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Meyer, A.
A1 - Weidner, Steffen
T1 - High Tm Poly(l-lactide)s by Means of Bismuth Catalysts?
N2 - One series of BiSub-catalyzed ring-opening polymerizations (ROPs) is per-formed at 160 °C for 3 days with addition of difunctional cocatalysts to find out, if poly(l-lactide) crystallizes directly from the reaction mixture. An analogous series is performed with monofunctional cocatalysts. High Tm crystal-lites (Tm > 190 °C) are obtained from all bifunctional cocatalysts, but not from all monofunctional ones. It is shown by means of SAXS measurements that the high Tm values are mainly a consequence of a transesterification–homogenization process across the lamellar surfaces resulting in thickness and smoothing of the surfaces. An unusual enthalpy-driven modification of the molecular weight distribution is found for samples that have crystallized during the polymerization. A third series of ROPs is performed at 170 °C for 2 h followed by annealing at 120 °C (2 h) to induce crystallization. Complete transformation of the resulting low Tm crystallites (Tm < 180 °C) into the high Tm crystallites by annealing at 170 °C for 1 d is not achieved, despite variation of the cocatalyst.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystallization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-522777
DO - https://doi.org/10.1002/macp.202100019
SN - 1022-1352
VL - 222
IS - 8
SP - 19
PB - Wiley
AN - OPUS4-52277
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - About the Influence of (Non-)Solvents on the Ring Expansion Polymerization of l-Lactide and the Formation of Extended Ring Crystals
N2 - Ring-expansion polymerizations (REPs) catalyzed by two cyclic tin catalysts(2-stanna-1.3-dioxa-4,5,6,7-dibenzazepine [SnBiph] and
2,2-dibutyl-2-stanna-1,3-dithiolane [DSTL) are performed at 140 °C in bulk.
Small amounts (4 vol%) of chlorobenzene or other solvents are added to facilitate transesterification reactions (ring–ring equilibration) in the solid poly(l-lactide)s. In the mass range up to m/z 13 000 crystalline PLAs displaying a so-called saw-tooth pattern in the MALDI-TOF mass spectra are obtained indicating the formation of extended-ring crystals. The characteristics of extended-ring crystallites and folded-ring crystallites are discussed. Furthermore, extremely high melting temperatures (Tm’s up to 201.2 °C) and melting enthalpies (𝚫Hm’s up to 106 J g−1)) are found confirming that 𝚫Hmmax, the 𝚫Hm of a perfect crystal, is around or above 115 J g−1 in contrast to literature data.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring-expansion polymerization
KW - Crystals
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565038
DO - https://doi.org/10.1002/macp.202200385
SN - 1022-1352
SP - 1
EP - 8
PB - Wiley VHC-Verlag
AN - OPUS4-56503
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H. R.
T1 - SnOct2-catalyzed ROPs of L-lactide initiated by acidic OH- compounds: Switching from ROP to polycondensation and cyclization
N2 - Ring-opening polymerizations (ROPs) of L-lactide are performed in bulk at 130°C with tin(II) 2-ethylhexanoate as catalyst and various phenols of differentacidity as initiators. Crystalline polylactides having phenyl ester end groups are isolated, which are almost free of cyclics. The dispersities and molecular weights are higher than those obtained from alcohol-initiated ROPs under identical conditions. Polymerizations at 160°C yield higher molecular weights than expected from the monomer/initiator ratio and a considerable fraction of cycles. The fraction of cycles increases with higher reactivity of the ester end group indicating that the cycles are formed by end-to-end cyclization.
KW - Polylactide
KW - MALDI-TOF MS
KW - Polymerization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-540250
DO - https://doi.org/10.1002/pol.20210823
SN - 2642-4150
VL - 60
IS - 5
SP - 785
EP - 793
PB - Wiley
AN - OPUS4-54025
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Werthmann, Barbara
A1 - Schröder, Hartmut
A1 - Just, Ulrich
A1 - Borowski, Renate
A1 - Decker, Renate
A1 - Schwarz, Bärbel
A1 - Schmücking, I.
A1 - Seifert, Ingetraut
T1 - A new approach of characterizing the hydrolytic degradation of poly(ethylene terephthalate) by MALDI-MS
N2 - The hydrolytic degradation of technical poly(ethylene terephthalate) (PET) was investigated by means of different methods such as size-exclusion chromatography (SEC), viscometry, light-scattering, thin-layer chromatography, end-group titration, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The long-term degradation was simulated by exposing PET filament yarns to aqueous neutral conditions at 90°C for up to 18 weeks. By means of MALDI-MS and thin-layer chromatography, the formation of different oligomers was obtained during polymer degradation. As expected, an ester scission process was found generating acid terminated oligomers (H-[GT]m-OH) and T-[GT]m-OH and ethylene glycol terminated oligomers (H-[GT]m-G), where G is an ethylene glycol unit and T is a terephthalic acid unit. Additionally, the scission of the ester bonds during the chemical treatment led to a strong decrease in the number of cyclic oligomers ([GT]m). The occurrence of di-acid terminated species demonstrated a high degree of degradation.
PY - 1997
DO - https://doi.org/10.1002/(SICI)1099-0518(199708)35:11<2183::AID-POLA9>3.0.CO;2-Z
SN - 0360-6376
SN - 0887-624X
VL - 35
IS - 11
SP - 2183
EP - 2192
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-11357
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Koprinarov, Ivaylo
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
ED - Nowack, H.
T1 - Wechselwirkungen zwischen plasmamodifizierten Polymeroberflächen und Metallen
T2 - 5. Internationale Fachtagung - ND-Plasma-Technologie
CY - Duisburg, Deutschland
DA - 1997-09-22
PY - 1997
VL - 5
SP - 1(?)
EP - 17(?)
PB - Print-Service
CY - Mülheim
AN - OPUS4-6995
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
T1 - Reversible Polycondensations outside the Jacobson-Stockmayer Theory and a New Concept of Reversible Polycondensations
N2 - L-Lactide was polymerized with tin(II)acetate, tin(II)2-ethyl hexanoate, diphenyltin dichloride and dibutyltin bis(pentafluorophenoxide) at 130 °C in bulk. When an alcohol was added as initiator, linear chains free of cycles were formed having a degree of polymerization (DP) according to the lactide/initiator (LA/In) ratio.
Analogous polymerizations in the absence of an initiator yielded high molar mass cyclic polylactides.
Quite similar results were obtained when ε-caprolactone was polymerized with or without initiator.
Several transesterification experiments were conducted at 130 °C, either with polylactide or poly(ε-caprolactone) indicating that several transesterification mechanisms are operating under conditions that do not include formation of cycles by back-biting. Furthermore, reversible polycondensations (revPOCs) with low or moderate conversions were found that did not involve any kind of cyclization. Therefore, These results demonstrate the existence of revPOCs, which do neither obey the theory of irreversible polycondensation as defined by Flory nor the hypothesis of revPOCs as defined by Jacobson and Stockmayer. A new concept encompassing any kind of revPOCs is formulated in the form of a “polycondensation triangle”.
KW - Polylactide
KW - MALDI-TOF MS
KW - Polycondensation
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-530831
DO - https://doi.org/10.1039/d1py00704a
VL - 12
IS - 35
SP - 5003
EP - 5016
PB - Royal Society for Chemistry
AN - OPUS4-53083
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - Poly(L-lactide): Optimization of Melting Temperature and Melting Enthalpy
N2 - Twice recrystallized L-lactide was polymerized with a dozen of different tin or bismuth catalysts in bulk at 160°C for 24 h and was annealed at 150°C afterwards. In two cases Tm values above 197.0°C were obtained. The parameters causing a scattering of the DSC data were studied and discussed. The samples prepared with SnCl2, 2,2-dibutyl-2-stanna-1,3-ditholane (DSTL) or cyclic tin(II) bisphenyldioxide (SnBiph) were subject to annealing programs with variation of time and temperatures, revealing that the Tm´s did not increase. However, an increase of Hm was achieved with maximum values in the range of 93-96 J g-1 corresponding to crystallinities off around 90%. Further studies were performed with once recrystallized L-lactide. Again, those samples directly crystallized from the polymerization process showed the highest Tm values. These data were compared with the equilibrium Tm0 and Hm0 data calculated by several research groups for perfect crystallites. A Tm0 of 213+/-2°C and a Hm0 of 106 J g-1 show the best agreement with the experimental data. The consequences of annealing for the thickness growth of crystallites are discussed on the basis of SAXS measurements. Finally, a comparison of cyclic and linear poly L-lactide)s is discussed.
KW - Polylactide
KW - MALDI-TOF MS
KW - Transesterification
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538656
DO - https://doi.org/10.1039/D1MA00957E
SP - 1
EP - 10
PB - Royal Society for Chemistry
AN - OPUS4-53865
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - High Tm linear poly(L-lactide)s prepared via alcohol-initiated ROPs of L-lactide
N2 - Alcohol-initiated ROPs of L-lactide were performed in bulk at 160 °C for 72 h with variation of the catalyst or with variation of the initiator (aliphatic alcohols). Spontaneous crystallization was only observed when cyclic Sn(II) compounds were used as a catalyst. Regardless of initiator, high melting crystallites with melting temperatures (Tm) of 189–193 °C were obtained in almost all experiments with Sn(II) 2,2′-dioxybiphenyl (SnBiph) as catalyst, even when the time was shortened to 24 h. These HTm poly(lactide)s represent the thermodynamically most stable form of poly(L-lactide). Regardless of the reaction conditions, such high melting crystallites were never obtained when Sn(II) 2-ethylhexanoate (SnOct2) was used as catalyst. SAXS measurements evidenced that formation of HTm poly(L-lactide) involves growth of the crystallite thickness, but chemical modification of the crystallite surface (smoothing) seems to be of greater importance. A hypothesis, why the “surface smoothing” is more effective for crystallites of linear chains than for crystallites composed of cycles is discussed.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring-opening polymerization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524330
DO - https://doi.org/10.1039/d1ra01990b
VL - 11
IS - 23
SP - 14093
EP - 14102
PB - Royal Society of Chemistry
AN - OPUS4-52433
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - ROP of L-lactide and ε-caprolactone catalyzed by tin(ii) andtin(iv) acetates–switching from COOH terminated linear chains to cycles
N2 - The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations of L-lactide conducted in bulk at 160 or 130°C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied and linear chains having one acetate and one carboxyl end group almost free of cyclics were obtained. Higher monomer/catalyst ratios and lower temperatures favored formation of cycles that reached weight average molecular weights (Mw's) between 100,000 and 2,500,000. SnAc4 yielded mixtures of cycles and linear species under all reaction conditions. Dibutyltin- and dioctyl tin bis-acetate yielded cyclic polylactides under most reaction conditions with Mw's in the range of 20,000–80,000. Ring-opening polymerizations performed with ε-caprolactone showed similar trends, but the formation of COOH-terminated linear chains was significantly more favored compared to analogous experiments with lactide. The reactivity of the acetate catalysts decreased in the following order: SnAc2> SnAc4>Bu2SnAc2~Oct2SnAc2
KW - Polylactide
KW - MALDI-TOF MS
KW - Catalyst
KW - Ring-opening polymerization
KW - Tin acetates
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521923
DO - https://doi.org/10.1002/pol.20200866
VL - 59
IS - 5
SP - 439
EP - 450
PB - Wiley Online Library
AN - OPUS4-52192
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Scheliga, F.
A1 - Weidner, Steffen
T1 - What does conversion mean in polymer science?
N2 - The definition of the term “conversion” is discussed for a variety of polymer syntheses. It is demonstrated that in contrast to organic and inorganic chemistry several different definitions are needed in polymer science. The influence of increasing conversion on structure and topology of homo- and Copolymers is illustrated. Chain-growth polymerizations, such as radical polymerization or living anionic polymerizations of vinyl monomers, condensative chain polymerization, two and three-dimensional step-growth polymerizations, ring–ring or chain–chain equilibration and chemical modification of polymers are considered.
KW - Polymers
KW - Polymerization
KW - Conversion
KW - Polycondensation
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523597
DO - https://doi.org/10.1002/macp.202100010
VL - 222
IS - 8
SP - 10
PB - Wiley VCH
AN - OPUS4-52359
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
T1 - The role of transesterifications in reversible polycondensations and a reinvestigation of the Jacobson-Beckmann-Stockmayer experiments
N2 - The polycondensations of adipic acid and 1,10-decanediol catalyzed by toluene sulfonic acid (TSA) were reinvestigated using MALDI TOF mass spectrometry and NMR spectroscopy. Unexpected reactions of TSA were detected along with incomplete conversion of the monomers. Furthermore, transesterification reactions of end-capped poly(1,10-decanediol adipate) and end-capped poly(ε-caprolactone) catalyzed by TSA were studied. Despite the quite different (ionic) reaction mechanisms, it was found that for polycondensations performed in bulk intermolecular transesterification is more efficient than the intramolecular “back-biting”; this scenario was not considered in the Jacobson–Stockmayer theory of reversible polycondensations.
These results also confirm that the Jacobson–Stockmayer explanation of reversible polycondensations solely on the basis of ring chain equilibration is not only devoid of any experimental evidence, but also in contradiction to the results elaborated in this work.
KW - Polylactide
KW - MALDI-TOF MS
KW - Polycondensation
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543402
DO - https://doi.org/10.1039/d1py01679b
SN - 1759-9962
SP - 1
EP - 9
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-54340
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Ring-Expansion Polymerization of 𝝐-Caprolactone, Glycolide, and l-lactide with a Spirocyclic Tin(IV) Catalyst Derived from or 2,2′-Dihydroxy-1,1′-Binaphthyl – New Results and a Revision
N2 - In contrast to other cyclic tin bisphenoxides, polymerizations of glycolide and l-lactide with the spirocyclic tin(IV) bis-1,1′-bisnapthoxide yield linear chains having a 1,1′-bisnapthol end group and no cycles. In the case of l-lactide, LA/Cat ratio and temperature are varied and at 160 °C or below, all polylactides mainly consist of even-numbered chains. A total predominance of even-numbered chains is also found for homopolymerization of glycolide, or the copolymerization of glycolide and l-lactide, when conducted <120 °C.
Linear chains having a bisnaphthol end group are again the main reaction products of ring-expansion polymerizations (REP) of 𝝐-caprolactone, but above 150 °C cycles are also formed.
KW - Polylactide
KW - MALDI-TOF MS
KW - Polymerization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-541931
DO - https://doi.org/10.1002/macp.202100308
VL - 222
IS - 24
SP - 1
EP - 10
PB - Wiley VCH GmbH
AN - OPUS4-54193
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
T1 - H2O-Initiated Polymerization of L-Lactide
N2 - Water-initiated ring-opening polymerizations (ROPs) of L-lactide (LA) were performed in bulk at 140 °C, whereupon 11 different salts or complexes of low-toxic metal ions such as tin (II), Zn(II), Zr(IV), and Bi(III) were used as catalysts. Only four catalysts gave satisfactory results despite a long reaction time (24 h). The influence of the temperature was studied with tin (II) 2-ethylhexanoate (SnOct2), dibutyltin oxide (Bu2SnO), and zinc bis-acetylacetonate (Zn(acac)2) and zirconium acetylacetonate (Zr(acac)4). With SnOct2, Bu2SnO and Zr(acac)4 the time was varied at 140 °C to compare their reactivity. Furthermore, two series of ROPs were carried out with variation of the LA/H2O ratio to verify the control of the molecular weight by the monomer-initiator ratio. Bi- or tri-modal molecular weight distributions (MWD) were found for most of the ROPs and bimodal melting endotherms in the differential scanning calorimetry (DSC) heating traces. The thickness and dependence of the 3D packing of the crystallites were monitored by small-angle X-ray scattering (SAXS) measurements.
KW - MALDI-TOF MS
KW - Polylactide
KW - Ring-opening polymerization
KW - Crystallization
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-628761
DO - https://doi.org/10.1007/s10924-025-03565-w
SN - 1572-8919
VL - 33
IS - 6
SP - 2843
EP - 2857
PB - Springer Science and Business Media LLC
CY - New York, NY
AN - OPUS4-62876
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Scheliga, Felix
A1 - Kricheldorf, Hans R.
T1 - Polycondensation, Cyclization and Disproportionation of Solid Poly(L-lactide) Trifluoroethyl Esters and the Simultaneous Formation of Extended Chain Crystals and Extended Ring Crystals
N2 - Two poly(L-lactide)s (PLAs) with a degree of polymerization (DP) of 20 or 100 were prepared by trifluoroethanol-initiated ring-opening polymerization (ROP) catalyzed by tin(II) 2-ethyl hexanoate (SnOct2). These PLAs were annealed at 140 ◦C or at 160 ◦C in the presence of SnOct2, and the changes in topology and molecular weight distribution (MWD) were monitored by matrix-assisted laser desorption/ionization time-of flight (MALDI TOF) mass spectrometry and gel permeation chromatography (GPC). For the PLA with a DP 20, the main reaction was polycondensation combined with higher dispersities. In the case of the DP 100, PLA polycondensation was combined with disproportionation and the formation of a new MWD maximum around m/z 3500. In addition, extensive cyclization occurred, and the resulting cyclic PLAs crystallized separately from the linear chains in the form of extended ring crystals. These results also suggest that both extended chain and extended ring crystals posses the same crystal thickness as a result of thermodynamically controlled transesterification in the solid state.
KW - Polycondensation
KW - MALDI
KW - Polylactide
KW - Cyclization
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-616441
DO - https://doi.org/10.1016/j.polymer.2024.127800
VL - 315
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-61644
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Falkenhagen, Jana
A1 - Dalgic, Mete-Sungur
A1 - Weidner, Steffen
T1 - Quantitative MALDI-TOF Mass Spectrometry of Star-Shaped Polylactides Based on Chromatographic Hyphenation
N2 - The end groups of three- and four-arm star-shaped polylactides (PLA) with trimethylolpropane and pentaerythritol core structures were functionalized with acetic acid. Reaction products with different degrees of functionalization were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Additional gradient elution liquid adsorption chromatography (GELAC) measurements were performed to determine the degree of functionalization. This technique enabled clear separation and sufficient quantification of the formed species. These chromatographic data could be used inversely to quantify mass spectrometric results, which are usually biased by the unknown ionization probabilities of different polymer end group structures. Our results showed that, in this particular case, the peak intensity in the MALDITOF mass spectra can be used to semiquantitatively determine the degree of functionalization in incompletely functionalized multiarm PLA.
KW - Polylactides
KW - MALDI-TOF-MS
KW - Gradient elution liquid adsorption chromatography
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625292
DO - https://doi.org/10.1021/jasms.4c00491
SN - 1879-1123
SP - 1
EP - 9
PB - American Chemical Society (ACS)
AN - OPUS4-62529
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
A1 - Scheliga, Felix
T1 - Polycondensation of L-lactic acid: a deeper look into solid state polycondensation
N2 - L-Lactic acid (LA) was condensed in the presence of SnCl2 or 4-toluenesulfonic acid (TSA) at 140 °C, and chain growth without cyclization was observed. In addition, poly(L-lactic acid)s (PLAs) with a degree of polymerization (DP) of 25, 50 or 100 were prepared by water-initiated ring-opening polymerization (ROP). These PLAs were annealed in the solid state at 140 °C and 160 °C in the presence of tin(II) 2-ethylhexanoate (SnOct2, SnCl2 or TSA). The changes in the molar mass distribution and in the topology were characterized by means of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and size exclusion chromatography (SEC). With increasing time, fewer side reactions caused higher molar masses and increasing fractions of cyclic polylactides (cPLA) were obtained. Their “saw tooth” pattern in the MALDI-TOF mass spectra indicated the formation of extended ring crystallites in the solid state. TSA was the most active catalyst and caused fewer side reactions than SnCl2, which was the least reactive catalyst. Acetylation of the CH-OH end groups hindered polycondensation and prevented the formation of cPLAs. Reaction mechanisms will be discussed.
KW - MALDI-TOF MS
KW - Polycondensation
KW - Polylaktide
KW - Solid state
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625271
DO - https://doi.org/10.1039/d4py01191k
SN - 1759-9962
SP - 1
EP - 9
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-62527
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - About alcohol-initiated polymerization of glycolide and separate crystallization of cyclic and linear polyglycolides
N2 - Alcohol-initiated polymerizations of glycolide (GL) catalyzed by tin(II) 2-ethylhexanoate (SnOct2) were carried out in bulk with variation of GA/In ratio, temperature and time. Due to a rather strong competition of cyclization polyglycolide (PGA) free of cycles were never obtained. When the cyclic catalysts 2,2-dibutal-2-stanna − 1,3-dithiolane (DSTL) or 2-stanna 1,3-dioxo-4,5,6,7 bibenzepane (SnBiph) were used in combination with 1,4-butanediol the influence of cyclization was even stronger. Furthermore, the degrees of polymerization were higher than the GA/alcohol ratio due to rapid polycondensation in the solid state. At 160 °C or below, the matrixassisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra indicated separate crystallization of low molar mass cyclic and linear PGAs from the same reaction mixture (also observed for poly(L-lactide)s).
KW - MALDI TOF MS
KW - Polyglycolide
KW - Ring opening polymerization
KW - Cyclization
KW - Crystallization
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-607282
DO - https://doi.org/10.1016/j.polymer.2024.127440
SN - 0032-3861
VL - 309
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-60728
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Syntheses of cyclic polylactides and the problem of catenane formation
N2 - Cyclic poly(L-lactide)s (PLAs) were prepared in bulk either by ring-expansion polymerization (REP) or by ring-opening polymerization (ROP) with simultaneous polycondensation (ROPPOC). In contrast to REP the latter method involves formation of linear chains and thus, may involve formation of polydisperse catenanes that affect crystallization. The reprecipitated PLAs were annealed at 120 °C and compared with regard to melting temperature (Tm) and melting enthalpy (ΔHm). For similar molar masses the PLAs prepared by REP and ROPPOC had almost identical Tm's and crystallinities. Furthermore, the influence of REP and ROPPOC catalysts on the morphology of the virgin reaction products was compared.
KW - MALDI-TOF MS
KW - Catenane
KW - Polylactide
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625061
DO - https://doi.org/10.1039/d4ra08683j
VL - 15
IS - 5
SP - 3686
EP - 3692
PB - RSC
AN - OPUS4-62506
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
ED - Barner-Kowollik, C.
ED - Gründling, T.
ED - Falkenhagen, Jana
ED - Weidner, Steffen
T1 - Hyphenated techniques
N2 - Hyphenation of techniques has become a versatile tool in polymer analysis. It has been demonstrated that the complexity and heterogeneity of modern polymers and copolymers, in particular, could only be determined by a combination of several methods. With this regard, a chromatographic separation in various thermodynamic modes combined with mass spectral identification of polymer species provides new insights in polymer synthesis, modification, and degradation. Both methods are widely complementary and can therefore often compensate each other’s drawbacks. The development of suitable coupling interfaces, the introduction of AP devices, and an increasing application of ESI pushed polymer analysis toward new regions. Future developments in the field of MS detectors, lasers and software, as well new pressure-stable stationary chromatographic phases will aid in increasing the importance and acceptance of LC-MS coupling methods and will enable new applications in sophisticated polymer analysis.
KW - MALDI
KW - Chromatography
KW - Coupling techniques
PY - 2012
SN - 978-3-527-32924-3
SN - 978-3-527-64182-6
DO - https://doi.org/10.1002/9783527641826.ch7
SP - 209
EP - 235
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-26395
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schmid, C.
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Barner-Kowollik, C.
T1 - In-depth LCCC-(GELC)-SEC characterization of ABA block copolymers generated by a mechanistic switch from RAFT to ROP
N2 - A recently introduced procedure involving a mechanistic switch from reversible addition–fragmentation chain transfer (RAFT) polymerization to ring-opening polymerization (ROP) to form diblock copolymers is applied to synthesize ABA (star) block copolymers. The synthetic steps include the polymerization of styrene with R-group designed RAFT agents, the transformation of the thiocarbonyl thio end groups into OH functionalities, and their subsequent chain extension by ROP. The obtained linear ABA poly(ε-caprolactone)-block-poly(styrene)-block-poly(ε-caprolactone) (pCL-b-pS-b-pCL) (12 500 g mol¯¹ ≤ Mₙ ≤ 33 000 g mol¯¹) and the star-shaped poly(styrene)-block-poly(ε-caprolactone) (Mₙ = 36 000 g mol¯¹) copolymers were analyzed by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), infrared (IR) spectroscopy, and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The focus of the current study is on the detailed characterization of the ABA (star) block polymers via multidimensional chromatographic techniques specifically high performance liquid chromatography coupled to size exclusion chromatography (HPLC-SEC). In particular, we demonstrate the first time separation of poly(ε-caprolactone) (pCL) homopolymer and additionally poly(styrene) (pS) from the ABA poly(ε-caprolactone)-b-poly(styrene)-b-poly(ε-caprolactone) and star-shaped poly(styrene)-b-poly(ε-caprolactone) block copolymer utilizing critical conditions (CC) for pCL with concomitant gradient elution liquid chromatography (GELC).
KW - Two-dimensional-liquid chromatography (2D-LC)
KW - Liquid chromatography under critical conditions (LCCC)
KW - Gradient elution liquid chromatography (GELC)
KW - Soft ionization mass spectrometry (ESI, MALDI)
KW - Reversible addition fragmentation chain transfer (RAFT)
KW - Ring opening polymerization (ROP)
PY - 2012
DO - https://doi.org/10.1021/ma2022452
SN - 0024-9297
SN - 1520-5835
VL - 45
IS - 1
SP - 87
EP - 99
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-25464
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - High molar mass cyclic poly(L-lactide)s by means of neat tin (II) 2-ethylhexanoate
N2 - L-lactide was polymerized in bulk at 120, 140, 160 and 180°C with neat tin(II) 2-ethylhexanoate (SnOct2) as catalyst. At 180°C the Lac/Cat ratio was varied from 25/1 up to 8 000/1 and at 160°C from 25/1 up to 6 000/1. The vast majority of the resulting polylactides consist of cycles in combination with a small fraction of linear chains having one octanoate and one COOH end group. The linear chains almost vanished at high Lac/Cat ratios, as evidenced by MALDI-TOF mass spectrometry and measurements of intrinsic viscosities and dn/dc values. At Lac/Cat ratios <1000/1 the number average molar masses (Mn) are far higher than expected for stoichiometic initiation, and above 400/1 the molar masses vary relatively little with the Lac/Cat ratio. At 180° slight discoloration even at short times and degradation of the molar masses were observed, but at 160°C or below colorless products with weight average molar masses (Mw) up to 310 000 g mol-1 were obtained. The formation of high molar mass cyclic polylactides is explained by a ROPPOC (Ring-Opening Polymerizatiom with simultaneous Polycondensation) mechanism with intermediate formation of linear chains having one Sn-O-CH end group and one mixed anhydride end group. Additional experiments with tin(II)acetate as catalyst confirm this interpretation. These findings together with the detection of several transesterification mechanisms confirm previous critique of the Jacobson-Stockmayer theory.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
PY - 2020
DO - https://doi.org/10.1039/d0py00811g
VL - 11
IS - 32
SP - 5249
EP - 5260
PB - Royal Society for Chemistry
AN - OPUS4-51130
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H.R.
A1 - Scheliga, F.
T1 - Cyclization and dispersity of poly(alkylene isophthalate)s
N2 - Poly(alkylene isophthalate)s were prepared by different methods, either in solution or in bulk. The SEC measurements were evaluated in such a way that all oligomers were included. In solution (monomer conc. 0.10.7 mol/L) large fractions of rings were formed and high dispersities (up to 12) were obtained, which disagree with theoretical predictions. Polycondensations in bulk did neither generate cyclics by 'back-biting' nor by end-to-end cyclization, when the maximum temperature was limited to 210 °C. The dispersities of these perfectly linear polyesters were again higher than the theoretical values. Regardless of the synthetic method monomeric cycles were never observed. Furthermore, SEC measurements performed in tetrahydrofuran and in chloroform and SEC measurements performed in three different institutes were compared. Finally, SEC measurements of five samples were performed with universal calibration and a correction factor of 0.71 ± 0.02 was found for normal calibration with polystyrene.
KW - Cyclization
KW - Polycondensation
KW - Polyesters
KW - Size exclusion chromatography
KW - Cyclics
KW - Dispersity
KW - SEC
KW - Universal calibration
KW - MALDI mass spectrometry
PY - 2016
DO - https://doi.org/10.1002/pola.27892
SN - 0360-6376
SN - 0887-624X
VL - 54
IS - 1
SP - 197
EP - 208
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-33731
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Grabicki, N.
A1 - Nguyen, K. T. G.
A1 - Weidner, Steffen
A1 - Dumele, O.
T1 - Confined Spaces in [n]Cyclo-2,7-pyrenylenes
N2 - A set of strained aromatic macrocycles based on [n]cyclo2,7-(4,5,9,10-tetrahydro)pyrenylenes is presented with size dependent photophysical properties. The K-region of pyrene was functionalized with ethylene glycol groups to decorate the outer rim and thereby confine the space inside the macrocycle. This confined space is especially pronounced for n = 5, which leads to an internal binding of up to 8.0×104 M–1 between the ether-decorated [5]cyclo-2,7-pyrenylene and shape complementary crown ether–cation complexes.
Both, the ether-decorated [n]cyclo-pyrenylenes as well as one of their host–guest complexes have been structurally characterized by single crystal X-ray analysis. In combination with computational methods the structural and thermodynamic reasons for the exceptionally strong binding have been elucidated. The presented rim confinement strategy makes cycloparaphenylenes an attractive supramolecular host family with a favorable, size-independent read-out signature and binding capabilities extending beyond fullerene guests.
KW - Cycloparaphenylenes
KW - Host–guest systems
KW - Macrocycles
KW - Molecular recognition
KW - Supramolecular chemistry
PY - 2021
DO - https://doi.org/10.1002/anie.202102809
SN - 1433-7851
VL - 60
IS - 27
SP - 1
EP - 7
PB - Wiley VCH
AN - OPUS4-52517
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Seifert, Stephan
A1 - Weidner, Steffen
A1 - Panne, Ulrich
A1 - Kneipp, Janina
T1 - Taxonomic relationship of pollen from MALDI TOF MS data using multivariate statistics
N2 - Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been suggested as a promising tool for the investigation of pollen, but the usefulness of this approach for classification and identification of pollen species has to be proven by an application to samples of varying taxonomic relations.
KW - MALDI mass spectrometry
KW - Pollen
KW - Multivariate statistics
PY - 2015
DO - https://doi.org/10.1002/rcm.7207
SN - 0951-4198
SN - 1097-0231
VL - 29
SP - 1145
EP - 1154
PB - Wiley
CY - Chichester
AN - OPUS4-35296
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gruendling, T.
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Barner-Kowollik, C.
T1 - Mass spectrometry in polymer chemistry: a state-of-the-art up-date
N2 - Two decades after the introduction of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), soft ionization mass spectrometry represents a powerful toolset for the structural investigation of synthetic polymers. The present review highlights the current state-of-the-art, covering the latest developments of novel techniques, enabling instrumentation as well as the important applications of soft ionization MS from the beginning of 2008. Special attention is paid to the role that soft ionization MS has played in the mechanistic investigation of radical polymerization processes since 2005.
KW - Polymerization mechanisms
KW - Mass spectrometry
KW - LC-MS coupling
PY - 2010
DO - https://doi.org/10.1039/b9py00347a
SN - 1759-9954
SN - 1759-9962
VL - 1
IS - 5
SP - 599
EP - 617
AN - OPUS4-21906
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Much, Helmut
A1 - Krüger, Ralph-Peter
A1 - Friedrich, Jörg Florian
T1 - Determination of chemical and molecular-weight distributions of heterogeneous polymers by means of MALDI-MS coupled with chromatography
T2 - 219th ACS national meeting
CY - San Francisco, CA, USA
DA - 2000-03-26
PY - 2000
SN - 0032-3934
VL - 41
IS - 1
SP - 655
EP - 656
PB - American Chemical Society
CY - Newark, NJ
AN - OPUS4-2169
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Beispiele für die Anwendung von MALDI-MS in der Polymeranalytik und zur Untersuchung von plasmamodifizierten Polymeroberflächen
T2 - Hoechst AG, Werk Kalle Albert
CY - Wiesbaden, Germany
DA - 1995-09-25
PY - 1995
AN - OPUS4-11274
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Mahoney, C. M.
A1 - Weidner, Steffen
ED - Barner-Kowollik, C.
ED - Gründling, T.
ED - Falkenhagen, Jana
ED - Weidner, Steffen
T1 - Surface analysis and imaging techniques
N2 - Over the past couple of decades, the field of imaging mass spectrometry has taken a quantum leap in the area of organic, polymeric, and biological analysis. SIMS, originally developed for characterization of inorganic materials and semiconductors, is now used on a regular basis for the surface and in-depth characterization of polymers and other soft samples. The recent development of cluster sources over the past 15 years has resulted in a major paradigm shift in SIMS, moving from 2-D to 3-D analysis in polymeric materials. MALDIs recent development of imaging methodology has made an overwhelming impact in the biological community. The ability to detect high-mass proteins and other organic compounds remains unrivaled. Furthermore, some of these instruments can now be operated under ambient pressure conditions, thus making it a much more versatile tool.
Although this is a time of expansion in the entire field of surface mass spectrometry, DESI and PDI methods are right at the beginning of their growth curve. It is expected, therefore, that significant developments will be observed in the coming years as these techniques mature. It has been said that these methods represent the future of desorption mass spectrometry. This is very likely to be true.
KW - Surface analysis
KW - Imaging techniques
PY - 2012
SN - 978-3-527-32924-3
SN - 978-3-527-64182-6
DO - https://doi.org/10.1002/9783527641826.ch6
SP - 149
EP - 207
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-26396
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Fischer, J.L.
A1 - Lutomski, C.A.
A1 - El-Baba, T.J.
A1 - Siriwardena-Mahanama, B.N.
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Allen, M. J.
A1 - Trimpin, S.
T1 - Matrix-assisted ionization-ion mobility spectrometry-mass spectrometry: Selective analysis of a europium-PEG complex in a crude mixture
N2 - The analytical utility of a new and simple to use ionization method, matrix-assisted ionization (MAI), coupled with ion mobility spectrometry (IMS) and mass spectrometry (MS) is used to characterize a 2-armed europium(III)-containing poly(ethylene glycol) (Eu-PEG) complex directly from a crude sample. MAI was used with the matrix 1,2-dicyanobenzene, which affords low chemical background relative to matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI). MAI provides high ion abundance of desired products in comparison to ESI and MALDI. Inductively coupled plasma-MS measurements were used to estimate a maximum of 10% of the crude sample by mass was the 2-arm Eu-PEG complex, supporting evidence of selective ionization of Eu-PEG complexes using the new MAI matrix, 1,2-dicyanobenzene. Multiply charged ions formed in MAI enhance the IMS gas-phase separation, especially relative to the singly charged ions observed with MALDI. Individual components are cleanly separated and readily identified, allowing characterization of the 2-arm Eu-PEG conjugate from a mixture of the 1-arm Eu-PEG complex and unreacted starting materials. Size-exclusion chromatography, liquid chromatography at critical conditions, MALDI-MS, ESI-MS, and ESI-IMS-MS had difficulties with this analysis, or failed.
KW - Matrix-assisted ionization ion mobility spectrometry mass spectrometry
KW - Europium
KW - Poly(ethylene glycol)
KW - Size-exclusion chromatography
KW - Liquid chromatography at critical conditions
KW - Electrospray ionization
KW - Matrix-assisted laser desorption/ionization
KW - Inductively coupled plasma-mass spectrometry
KW - ESI
KW - MALDI
KW - SEC
PY - 2015
DO - https://doi.org/10.1007/s13361-015-1233-8
SN - 1044-0305
VL - 26
IS - 12
SP - 2086
EP - 2095
PB - Elsevier
CY - New York, NY
AN - OPUS4-35283
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lauer, Franziska
A1 - Seifert, Stephan
A1 - Kneipp, Janina
A1 - Weidner, Steffen
T1 - Simplifying the preparation of pollen grains for MALDI-TOF MS classification
N2 - Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) is a well-implemented analytical technique for the investigation of complex biological samples. In MS, the sample preparation strategy is decisive for the success of the measurements. Here, sample preparation processes and target materials for the investigation of different pollen grains are compared. A reduced and optimized sample preparation process prior to MALDI-TOF measurement is presented using conductive carbon tape as target. The application of conductive tape yields in enhanced absolute signal intensities and mass spectral pattern information, which leads to a clear separation in subsequent pattern analysis. The results will be used to improve the taxonomic differentiation and identification, and might be useful for the development of a simple routine method to identify pollen based on mass spectrometry.
KW - MALDI
KW - Conductive carbon tape
KW - Pollen
KW - Sample pretreatment
KW - Principal component analysis
PY - 2017
DO - https://doi.org/10.3390/ijms18030543
SN - 1422-0067
SN - 1661-6596
VL - 18
IS - 3
SP - 543-1
EP - 543-11
PB - MDPI
AN - OPUS4-41733
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lahcini, M.
A1 - Weidner, Steffen
A1 - Oumayama, J.
A1 - Scheliga, F.
A1 - Kricheldorf, H. R.
T1 - Unsaturated Copolyesters of Lactide
N2 - Four classes of unsaturated copolyesters of L-lactide were prepared either from isosorbide or bis(hydroxymethyl)tricyclodecane in combination with fumaric acid or from 1,4-butenediol or 1,4- butynediol with terephthalic acid. All syntheses were performed in such a way that lactide was oligomerized with a diol as the initiator and the resulting oligomers were polycondensed with a dicarboxylic acid dichloride either in a one-pot synthesis or in a two-step procedure. For most copolyesters the SEC measurements gave weight average molecular weights in the range of 30–60 kg mol⁻1 and dispersities in the range of 4.2–6.2. The MALDI-TOF mass spectra displayed a high content of cycles and indicated an irreversible kinetic course of all polycondensations. Glass-transition temperatures (Tg) above 90 °C were only found for two copolyesters of isosorbide. Addition of bromine to copolyesters of 1,4-butenediol yielded flame retarding biodegradable polymers.
KW - Copolyester
KW - MALDI-TOF MS
KW - SEC
KW - Lactide
PY - 2016
DO - https://doi.org/10.1039/c6ra16008e
VL - 2016/6
IS - 96
SP - 93496
EP - 93504
PB - Royal Society of Chemistry
AN - OPUS4-37913
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Differences in MALDI Ionization of neat linear and cyclic poly(L-lactide)s
N2 - In addition to molar mass distribution (MMD) synthetic polymers often exhibit an additional chemical heterogeneity distribution, expressed by different end groups and other structural variations (e.g. tacticity, copolymer composition etc.). Ionization in MALDI MS is always strongly affected by such chemical properties. For example, the abundance of cyclics in MALDI TOF mass spectra is frequently reported to greatly exceed that of linears. Thus, the MALDI ionization behavior of various neat end-capped linear poly(L-lactide)s and one cyclic poly(L-lactide) was investigated and compared with that of blends of both structures. Moreover, the influence of the cationizing salt was investigated too.
Neat compounds and various blends of cyclic and linear species were prepared and studied using two MALDI TOF mass spectrometers under identical conditions with regard to sample preparation and instrumental conditions, except for the laser power and the salt used for cationization. Polymer samples were additionally characterized by NMR and SEC.
The steady increase of the laser intensity caused an exponential increase of the peak intensities of both linear and cyclic polylactides.The response of linear polylactides (in the investigated molecular mass range), whether as neat polymer or in blends with other linear polylactides was almost similar. This clearly supports our assumption that ionization in MALDI is probably unaffected by the end group structure.The variation of the laser power shows only little effect on the intensity ratio of linear-to linear and cyclic-to-linear polylactides in blends. Whereas neat linear polylactides at all laser intensities have a significantly higher abundance than neat cyclics, in mixtures of both an overestimation of cyclic species in MALDI TOF mass spectra of polylactides was found. However, this is far less distinct than frequently reported for other polymers.Concluding, peak suppression of linear polymers in mixtures of both architectures can be excluded, which also means, that polylactides showing only peaks of cyclic compounds in their MALDI - TOF mass spectra do not contain a significant fraction of linear analogues.
Our study is the first systematic comparison of the MALDI ionization of neat and blended cyclic and linear polylactides.
T2 - ASMS 2020 Reboot
CY - Online meeting
DA - 01.06.2020
KW - MALDI
KW - Ionization
KW - Linear
KW - Cyclic
KW - Polylactide
PY - 2020
AN - OPUS4-50852
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Kühn, Gerhard
A1 - Ghode, Archana
A1 - Weidner, Steffen
A1 - Retzko, Iris
A1 - Unger, Wolfgang
A1 - Friedrich, Jörg Florian
ED - Mittal, K. L.
T1 - Chemically well-defined surface functionalization of polyethylene and polypropylene by pulsed plasma modification followed by grafting of molecules
T2 - 2nd International Symposium on Polymer Surface Modification: Relevance to Adhesion
CY - Newark, NJ, USA
DA - 1999-05-24
KW - Plasma modification
KW - Chemical conversion of functional groups
KW - Spacers
KW - Polypropylene
KW - Polyethylene
PY - 2000
SN - 90-6764-327-0
VL - 2
SP - 45
EP - 64
PB - VSP
CY - Utrecht
AN - OPUS4-6975
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Friedrich, Jörg Florian
A1 - Gerstung, Vanessa
A1 - Mix, Renate
A1 - Kühn, Gerhard
A1 - Weidner, Steffen
ED - d'Agostino, R.
T1 - Pulsed plasma initiated homo- and copolymerisation - molar masses
T2 - 16th International Symposium on Plasma Chemistry (ISPC-16)
CY - Taormina, Italy
DA - 2003-06-22
PY - 2003
IS - CD-ROM
PB - Dep. of Chemistry, Univ.
CY - Bari
AN - OPUS4-2710
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF mass spectrometry for the analysis of synthetic polymers
T2 - eingelad. Vortrag im National Institute for Advanced Industrial Science and Technology (AIST)
CY - Tsukuba, Japan
DA - 2006-09-14
PY - 2006
AN - OPUS4-13827
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Cyclic Polylactides via Simultaneous Ring-Opening Polymerization and Polycondensation Catalyzed by Dibutyltin Mercaptides
N2 - L-Lactide is polymerized in bulk at 160 8C either with dibutyltin bis(benzylmercaptide) (SnSBzl), dibutyltin bis(benzothiazole 2-mercaptide) (SnMBT), or with dibutyltin bis(pentafluorothiophenolate) (SnSPF) as catalysts. SnSBzl yields linear polylactides having benzylthio-ester end groups in addition to cyclic polylactides, whereas SnMBT and SnSPF mainly or exclusively yield cyclic polylactides. This finding, together with model reactions, indicates that the SnS catalysts promote a combined ring-opening polymerization and polycondensation process including end-to-end cyclization. SnMBT caused slight racemization (3%–5%), when used at 160 8C. With SnSPF optically pure cyclic poly(L-lactide)s with high-molecular weights can be prepared at 160 8C.
KW - Cyclopolymerization
KW - Catalysts
KW - MALDI-TOF MS
KW - Polyester
KW - Ring-opening polymerization
PY - 2017
DO - https://doi.org/10.1002/pola.28762
VL - 55
IS - 22
SP - 3767
EP - 3775
PB - Wiley Periodicals
AN - OPUS4-42600
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI Mass spectrometry of synthetic polymers – making molecular elephants to fly
N2 - The importance of MALDI TOF mass spectrometry for the analysis of synthetic polymers is shown and some specific issues influencing the analysis e.g. polymer mass dispersity, matrix and matrix homogeneity, nature of cations and end groups, sequence distribution are discussed by means of examples.
T2 - Merck Polymer Seminar
CY - Online meeting
DA - 29.04.2021
KW - MALDI-ToF MS
KW - Ionization
KW - Desorption
KW - Polymers
PY - 2021
AN - OPUS4-52545
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF-MS of low-molar mass polyethylene and waxes
T2 - 49th Conference of the American Society of Mass Spectrometry
CY - Chicago, IL, USA
DA - 2001-05-25
PY - 2001
AN - OPUS4-11302
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Trimpin, S.
A1 - Lee, C.
A1 - Weidner, Steffen
A1 - El-Baba, T.
A1 - Lutomski, C.
A1 - Inutan, E.
A1 - Foley, C.
A1 - Ni, C.-K.
A1 - McEwen, C.
T1 - Unprecedented Ionization Processes in Mass SpectrometryProvide Missing Link between ESI and MALDI
N2 - In the field of mass spectrometry,producing intact, highly-charged protein ions from surfaces is a conundrum with significant potential payoff in application areas ranging from bio-medical to clinical research. Here, we report on the ability to form intact, highly-charged protein ions on high vacuum time-of-flight mass spectrometers in the linear and reflectron modes achievable using experimental conditions that allow effective matrix removal from both the sample surfaces and from the charged clusters formed by the laser Ablation event. The charge states are the highest reported on high vacuum mass spectrometers, yet they remain at only around athird of the highest charge obtained using laser ablation with a suitable matrix at atmospheric pressure. Other than physical instrument modifications, the key to forming abundant and stable highly-charged ions appears to be the volatility of the matrix used. Cumulative results suggest mechanistic links between the ionization process reported here and traditional ionization methods of electrospray ionization and matrix-assisted laser desorp-tion/ionization.
KW - MALDI
KW - Electrospray
KW - Mass spectrometry
KW - Ionization
PY - 2018
DO - https://doi.org/10.1002/cphc.201701246
SN - 1439-4235
SN - 1439-7641
VL - 19
IS - 5
SP - 581
EP - 589
PB - Wiley-VCH
AN - OPUS4-44404
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lee, C.
A1 - Inutan, E. D.
A1 - Chen, J. L.
A1 - Mukeku, M. M.
A1 - Weidner, Steffen
A1 - Trimpin, S.
A1 - Ni, C.-K.
T1 - Toward understanding the ionization mechanism of matrix‐assisted ionization using mass spectrometry experiment and theory
N2 - Matrix‐assisted ionization (MAI) mass spectrometry does not require voltages, a laser beam, or added heat to initiate ionization, but it is strongly dependent on the choice of matrix and the vacuum conditions. High charge state distributions of nonvolatile analyte ions produced by MAI suggest that the ionization mechanism may be similar to that of electrospray ionization (ESI), but different from matrix‐assisted laser desorption/ionization (MALDI). While significant information is available for MAI using mass spectrometers operating at atmospheric and intermediate pressure, little is known about the mechanism at high vacuum.
Eleven MAI matrices were studied on a high‐vacuum time‐of‐flight (TOF) mass spectrometer using a 266 nm pulsed laser beam under otherwise typical MALDI conditions. Detailed comparisons with the commonly used MALDI matrices and theoretical prediction were made for 3‐nitrobenzonitrile (3‐NBN), which is the only MAI matrix that works well in high vacuum when irradiated with a laser.
Screening of MAI matrices with good absorption at 266 nm but with various degrees of volatility and laser energies suggests that volatility and absorption at the laser wavelength may be necessary, but not sufficient, criteria to explain the formation of multiply charged analyte ions. 3‐NBN produces intact, highly charged ions of nonvolatile analytes in high‐vacuum TOF with the use of a laser, demonstrating that ESI‐like ions can be produced in high vacuum. Theoretical calculations and mass spectra suggest that thermally induced proton transfer, which is the major ionization mechanism in MALDI, is not important with the 3‐NBN matrix at 266 nm laser wavelength. 3‐NBN:analyte crystal morphology is, however, important in ion generation in high vacuum.
The 3‐NBN MAI matrix produces intact, highly charged ions of nonvolatile compounds in high‐vacuum TOF mass spectrometers with the aid of ablation and/or heating by laser irradiation, and shows a different ionization mechanism from that of typical MALDI matrices.
KW - Ionization
KW - MALDI-TOF MS
KW - Mechanism
PY - 2021
DO - https://doi.org/10.1002/rcm.8382
VL - 35
IS - 51
SP - e8382
PB - John Wiley & Sons
AN - OPUS4-49209
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Schultze, R.-D.
A1 - Enthaler, B.
T1 - Matrix-assisted laser desorption/ionization imaging mass spectrometry of pollen grains and their mixtures
N2 - RATIONALE
The fast and univocal identification of different species in mixtures of pollen grains is still a challenge. Apart from microscopic evaluation and Raman spectroscopy, no other techniques are available.
METHODS
Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry was applied to the analysis of extracts of single pollen grains and pollen mixtures. Pollen grains were fixed, treated and covered with matrix directly on the MALDI target.
RESULTS
Clearly resolved MALDI ion intensity images could be obtained enabling the identification of single pollen grains in a mixture.
CONCLUSIONS
Our results demonstrate the potential and the suitability of MALDI imaging mass spectrometry as an additional method for the identification of pollen mixtures.
KW - MALDI
KW - Imaging
KW - Pollen
KW - Blends
PY - 2013
DO - https://doi.org/10.1002/rcm.6523
SN - 0951-4198
SN - 1097-0231
VL - 27
IS - 8
SP - 896
EP - 903
PB - Wiley
CY - Chichester
AN - OPUS4-27986
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Leiterer, Jork
A1 - Panne, Ulrich
A1 - Thünemann, Andreas
A1 - Weidner, Steffen
T1 - Container-less polymerization in acoustically levitated droplets: an analytical study by GPC and MALDI-TOF mass spectrometry
N2 - Molecular masses and end groups of polystyrene (PS) formed in a novel container-less polymerization strategy, based on levitated droplets in an acoustic trap, were determined by Gel Permeation Chromatography (GPC) and Matrix-assisted Laser Desorption/Ionization Time of Flight Mass spectrometry (MALDI-TOF MS).
KW - Ultraschallfalle
KW - MALDI Massenspektrometrie
KW - Polymerisation
PY - 2011
DO - https://doi.org/10.1039/c0ay00390e
SN - 1759-9660
SN - 1759-9679
VL - 3
IS - 1
SP - 70
EP - 73
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-23655
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Neue Wege zur analytischen Charakterisierung komplexer Polymersysteme
T2 - Berliner Polymerentage 2000
CY - Berlin, Germany
DA - 2000-10-09
PY - 2000
AN - OPUS4-11134
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Falkenhagen, Jana
A1 - Kricheldorf, H. R.
T1 - SnOct2-catalyzed and alcohol-initiated ROPs of L-lactide – About the influence of initiators on chemical reactions in the melt and the solid state
N2 - SnOct2 (Sn(II) 2-ethylhexanoate) catalyzed ROPs of L-lactide were performed in bulk with eight different alcohols as initiators. The time was varied between 1 h and 24 h for all initiators. For two initiators the temperature was also lowered to 115 ◦C. Even-numbered chains were predominantly formed in all polymerizations at short times, but the rate of transesterification (e.g. even/odd equilibration) and the molecular weight distribution were found to depend significantly on the nature of the initiator. Observed transesterification reactions also continued in solid poly (L-lactide), and with the most active initiator, almost total equilibration was achieved even at 130 ◦C. This means that all chains including those of the crystallites were involved in transesterification reactions proceeding across the flat surfaces of the crystallites. The more or less equilibrated crystalline polylactides were characterized by DSC and SAXS measurements with regard to their melting temperature (Tm), crystallinity and crystal thickness.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystallization
KW - Catalysts
KW - SAXS
PY - 2021
DO - https://doi.org/10.1016/j.eurpolymj.2021.110508
VL - 153
SP - 110508
PB - Elsevier Ltd.
AN - OPUS4-52633
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Meyer, A.
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - ROPs of L-lactide catalyzed by neat Tin(II)2-ethylhexanoate - Influence of the reaction conditions on Tm and ΔHm
N2 - L-Lactide was polymerized by means of neat SnOct2 with variation of LA/Cat ratio, temperature and time. The resulting cyclic polylactides crystallized spontaneously at 160 °C or below, but needed nucleation via mechanical stress at 165 or 170 °C. All the crystalline polylactides obtained directly from ROP above 120 °C had melting temperatures (Tm) above 189 °C (up to 194.5 °C). SnOct2 also enabled transformation of low Tm poly(L-lactide)s (Tm <180 °C) into the high Tm m1odification by annealing, due to the impact of transesterification reactions in the interphase between the crystallites. The influence of crystallization temperature and annealing time on the crystal thickness was studied via SAXS measurements. A comparison with the crystallization and annealing experiments reported by Pennings and coworkers and Tsuji and Ikada is discussed, and a satisfactory agreement has been found, because those authors also studied polyLA samples containing SnOct2 in its active form. It is also demonstrated in this work that the high Tm modification cannot be obtained when the catalyst is removed or poisoned as it is true for commercial polylactides.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystallization
PY - 2021
DO - https://doi.org/10.1016/j.polymer.2021.124122
SN - 0032-3861
VL - 231
SP - 1
EP - 10
PB - Elsevier
CY - Oxford
AN - OPUS4-53194
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Baumann, Maria
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
A1 - Wold, C.
A1 - Uliyanchenko, E.
T1 - Characterization of copolymers of polycarbonate and polydimethylsiloxane by 2D chromatographic separation, MALDI-TOF mass spectrometry, and FTIR spectroscopy
N2 - The structure and composition of polycarbonate polydimethylsiloxane copolymer (PC-co-PDMS) was investigated by applying various analytical approaches including chromatographic separation methods, spectrometric, and spectroscopic detection techniques. In particular, size exclusion chromatography (SEC) and liquid adsorption chromatography operating at different conditions (e.g. using gradient solvent systems) were used to achieve separations according to molar mass and functionality distribution. The coupling of both techniques resulted in fingerprint two-dimensional plots, which could be used to easily compare different copolymer batches. Matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry was applied for structural investigations. The different ionization behavior of both comonomers, however, strongly limited the applicability of this technique. In contrast to that, Fourier-transform Infrared (FTIR) spectroscopy could be used to quantify the amount of PDMS in the copolymer at different points in the chromatogram. The resulting methodology was capable of distinguishing PC-co-PDMS copolymer from PC homopolymer chains present in the material.
KW - FTIR
KW - Liquid chromatography
KW - Mass spectrometry
KW - Gradient elution
KW - Polycarbonate-co-dimethylsiloxane copolymer
PY - 2020
DO - https://doi.org/10.1080/1023666X.2020.1820170
VL - 25
IS - 7
SP - 1
EP - 12
PB - Taylor & Francis
AN - OPUS4-51369
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H. R.
T1 - Spirocyclic bisphenoxides of Ge, Zr, and Sn as catalysts for ring-expansion polymerizations of L- and meso-lactide
N2 - Spirocyclic phenoxides of germanium, zirconium, and tin were prepared from 2,20-dihydroxybiphenyl and 2,20-dihydroxy-1,10-binaphthyl. Ring-expansion polymerizations of L-lactide are mainly studied at 160 or 180 °C. The reactivity of the catalysts increases in the order: Zr < Ge < Sn. Regardless of catalyst, the weight-average molecular weights (Mw) never exceed 50,000 g mol−1. The resulting poly(L-lactide)s are optically pure and have a cyclic architecture. Decreasing temperature and time favor Formation of even-numbered cycles, and at 102 ° cyclics, almost free of odd-numbered rings are obtained. Analogous polymerizations of meso-lactide give similar results >120 °C, but different results at 100 or 80 °C. Surprisingly, bell-shaped narrow molecular weight distributions are obtained <140 °C, resembling the pattern of living polymerizations found for alcohol-initiated polymerizations. An unusual transesterification mechanism yielding narrow distributions of odd-numbered cycles is discovered too.
KW - Cyclization
KW - Polylactides
KW - MALDI-TOF MS
KW - Ring-opening polymerization
KW - Spirocyclic
PY - 2018
DO - https://doi.org/10.1002/pola.29259
SN - 0887-624X
SN - 1099-0518
VL - 56
IS - 24
SP - 2730
EP - 2738
PB - Wiley Periodicals
AN - OPUS4-46498
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Polymer mass spectrometry at BAM with special emphasis on MALDI and ESI
N2 - Since its introduction mass spectrometric techniques like Matrix-assisted Laser Desorption/ionization (MALDI) and Electrospray Ionization (ESI) have become indispensable for synthetic polymer analyses. Ideally, various polymer properties (monomer structure, masses, mass distribution, end groups) can be determined simultaneously. However, in real life these experiments are always affected by important structural parameters and instrumental limitations.
A short introduction focussing on latest findings with respect to ionisation principles and mechanisms will be given. Recent results from our group will be presented and efforts to avoid common drawbacks of polymer mass spectrometry will be discussed. In this regard, MALDI - Imaging mass spectrometry and the 2D hyphenation of MS with different chromatographic separation techniques were especially useful, since they can provide additional information and reduce the complexity of polymer analyses.
T2 - 21. European Symposium on Polymer Spectroscopy
CY - Linz, Austria
DA - 13.01.2020
KW - Mass spectrometry
KW - MALDI-TOF MS
KW - ESI-TOF MS
KW - Polymer
PY - 2020
AN - OPUS4-50260
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Modifizierung plasmabehandelter Polyolefinoberflächen mit kovalent gebundenen Funktionsmolekülen
T2 - Workshop "Medicine meets Material", TEMA Berlin, Institut für Nichtmetallische Werkstoffe der TU Berlin
CY - Berlin, Germany
DA - 1999-01-29
PY - 1999
AN - OPUS4-11312
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wessig, P.
A1 - Schulze, T.
A1 - Pfennig, A.
A1 - Weidner, Steffen
A1 - Prentzel, S.
A1 - Schlaad, H.
T1 - Thiol–ene polymerization of oligospiroketal rods
N2 - The nucleophilic thiol–ene (thia-Michael) reaction between molecular rods bearing terminal thiols and bis-maleimides was investigated. The molecular rods have oligospiroketal (OSK) and oligospirothioketal (OSTK) backbones. Contrary to the expectations, cyclic oligomers were always obtained instead of linear rigid-rod polymers. Replacing the OS(T)K rods with a flexible chain yielded polymeric products, suggesting that the OS(T)K structure is responsible for the formation of cyclic products. The reason for the preferred formation of cyclic products is due to the presence of folded conformations, which have already been described for articulated rods.
KW - Oligospiroketals
KW - Polymerization
KW - MALDI-TOF MS
PY - 2017
DO - https://doi.org/10.1039/C7PY01569K
SN - 1759-9954
SN - 1759-9962
VL - 8
IS - 44
SP - 6879
EP - 6885
PB - Royal Society of Chemistry
AN - OPUS4-42685
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, Hans R.
T1 - Transesterification in the solid state of cyclic and linear poly(l-lactide)s
N2 - Poly(l-lactide)s are synthesized and annealed at 120 °C and changes of the molecular weight distribution (MWD) are monitored by matrix-assited laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. For example, benzyl alcohol+SnOct2 causes equilibration of odd- and even-numbered chains and the final goal of the transesterification is the most probable distribution. The underlying intermolecular transesterification is even observed at 100 and 80 °C in the solid state. However, cyclic tin mercaptide catalysts transform the initial most probable distribution into a MWD with maxima, which display a conspicuous fine structure due to a preferential crystallization of certain ring sizes. The optimum ring sizes for the crystallization are provided by ring-ring equilibration. The gradual formation of a special morphology shifts the melting temperature to values up to 187 °C. Annealing of commercial poly(l-lactide) with a cyclic tin catalyst also yields a distribution of mass peaks with a maximum showing the characteristic fine structure.
KW - Equilibration
KW - Mass spectrometry
KW - Polylactides
KW - Ring-opening polymerization
KW - Transesterification
PY - 2017
DO - https://doi.org/10.1002/macp.201700114
SN - 1521-3935
SN - 1022-1352
VL - 218
IS - 14
SP - 1700114-1
EP - 1700114-10
PB - Wiley-VCH
AN - OPUS4-41732
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Falkenhagen, Jana
A1 - Friedrich, Jörg Florian
A1 - Schulz, Günter
A1 - Krüger, Ralph-Peter
A1 - Much, Helmut
A1 - Weidner, Steffen
T1 - Liquid Adsorption Chromatography near Critical Conditions of Adsorption coupled with Matrix-assisted Laser Desorption/Ionization Mass Spectrometry
N2 - Chemical heterogeneities and molecular weight distributions of poly(ethylene oxide) (PEO)-co-polymethylene (PM) model oligomers, which are relevant to the synthesis of commonly used tensides, were investigated. For analytical characterization, the well-known principle of liquid adsorption chromatography at 'critical conditions' (LACCC) was modified. Near the critical conditions of adsorption of the PEO unit, e.g., at slight adsorption conditions of PM, the copolymers could be separated according to their PM chain length. The eluates were separated and single fractions of each peak were continuously transferred onto the MALDI target by means of a commercially available device. Simultaneously, the MALDI matrix solution was continuously added with a second pump. This procedure offers the possibility of the formation of homogeneous matrix-polymer textures. By MALDI-MS a complete characterization of the chemical composition (PEO and PM chain length) of each peak could be achieved. The obtained MALDI mass spectra of the eluates at different retention times could be used for the molecular weight calibration of the LAC system. In this way, an additional application of SEC, as in conventional 2D-chromatography, was avoided by using the MALDI method as quasi chromatographic separation
KW - Liquid adsorption chromatography
KW - Matrix-assisted laser desorption
KW - Ionization mass spectrometry
KW - Coupling methods
KW - MALDI
PY - 2000
DO - https://doi.org/10.1080/10236660008034644
SN - 1023-666X
SN - 1563-5341
VL - 5
SP - 549
EP - 562
PB - Gordon and Breach Publ.
CY - Amsterdam
AN - OPUS4-2168
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Just, Ulrich
A1 - Wittke, Wolfgang
A1 - Rittig, F.
A1 - Gruber, F.
A1 - Friedrich, Jörg Florian
T1 - Analysis of modified polyamide 6.6 using coupled liquid chromatography and MALDI-TOF-mass spectrometry
KW - MALDI-TOF-MS
KW - Liquid chromatography
KW - Coupling methods
PY - 2004
SN - 0168-1176
SN - 0020-7381
SN - 1387-3806
SN - 1873-2798
VL - 238
IS - 3
SP - 235
EP - 244
PB - Elsevier
CY - Amsterdam
AN - OPUS4-6966
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Knappe, Patrick
A1 - Panne, Ulrich
T1 - MALDI-TOF imaging mass spectrometry of artifacts in 'dried droplet' polymer samples
N2 - Matrix-assisted laser desorption/ionization-timeof-flight (MALDI-TOF) imaging of polystyrenes with various molecular masses was applied to study spatial molecular mass distribution of polymers in sample spots prepared by the 'dried droplet' method. When different solvents and target surfaces were examined, a segregation of single homologous polymers was observed depending upon the evaporation rate of the solvent. For the observed Patterns left by the evaporating droplet, a hypothesis is offered taking into account different hydrodynamic interactions and diffusion.
The results illustrate that spot preparation using the conventionally 'dried droplet' method is prone to artifacts and should be avoided for reliable and reproducible MALDI mass spectrometry experiments with regards to the Determination of molecular masses and mass distributions.
KW - MALDI
KW - Mass spectrometry imaging
KW - Polymer
KW - Droplet
PY - 2011
DO - https://doi.org/10.1007/s00216-011-4773-1
SN - 1618-2642
SN - 1618-2650
VL - 401
IS - 1
SP - 127
EP - 134
PB - Springer
CY - Berlin
AN - OPUS4-24538
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gille, M.
A1 - Viertel, A.
A1 - Weidner, Steffen
A1 - Hecht, S.
T1 - Modular synthesis of monomers for on-surface polymerization to graphene architectures
N2 - We developed a modular synthesis of halogenated polycyclic aromatic monomers for on-surface polymerization to generate graphene wires, ribbons, and networks.
KW - Graphene monomers
KW - Graphene nanoribbons
KW - Functionalized graphene nanoribbons
KW - Graphene wires
KW - Hexabenzocoronene
KW - On-surface polymerization
PY - 2013
DO - https://doi.org/10.1055/s-0032-1317959
SN - 0936-5214
SN - 1437-2096
VL - 24
IS - 2
SP - 0259
EP - 0263
PB - Thieme
CY - Stuttgart
AN - OPUS4-27621
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Just, Ulrich
T1 - Characterization of oligomers in poly(ethylene terephthalate) by matrix-assisted laser desorption/ionization mass spectrometry
PY - 1995
SN - 0951-4198
SN - 1097-0231
IS - 9
SP - 697
EP - 702
PB - Wiley
CY - Chichester
AN - OPUS4-11278
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-MS zur Charakterisierung der Oligomeren nach hydrolytischem und plasmachemischem Abbau von Polymeren
T2 - I. BAM-Kolloquium zu "Anwendung von MALDI-MS zur Charakterisierung von synthetischen Polymeren"
CY - Berlin, Germany
DA - 1997-06-02
PY - 1997
AN - OPUS4-11276
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF-MS zur Analytik von synthetischen Polymeren
T2 - Seminar zur Makromolekularen Chemie im SS 1999, TU Berlin, AK Prof. Springer
CY - Berlin, Germany
DA - 1999-11-13
PY - 1999
AN - OPUS4-11300
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kühn, Gerhard
A1 - Weidner, Steffen
A1 - Just, Ulrich
A1 - Hohner, G.
T1 - Characterization of technical waxes - Comparison of chromatographic techniques and matrix-assisted laser-desorption/ionization mass spectrometry
N2 - Technical waxes and paraffins were investigated using supercritical fluid chromatography (SFC), matrix-assisted laser-desorption/ionization mass spectrometry (MALDI-MS) and size-exclusion chromatography (SEC). SEC enables the simultaneous determination of molecular masses up to high values and molecular mass distributions. The resolution of homologous species, however, is poor. In this respect the use of SFC is advantageous. Proper resolution of homologues may be provided up to Mr~1200 without great difficulty. To compare these chromatographic results MALDI-MS was applied for the determination of molecular masses and mass distributions in technical waxes for the first time. Using reflectron mode excellent MALDI mass spectra could be achieved in the molecular mass range up to 1000 Da. The mean values of the molecular masses calculated by MALDI-MS were in sufficient agreement with those of SFC. In the linear mode of MALDI-MS molecular masses could be determined to nearly 3000 Da. Beyond this mass range SEC still remains the method of choice. Advantages and difficulties of the used methods are discussed in this paper.
PY - 1996
DO - https://doi.org/10.1016/0021-9673(95)01255-9
SN - 0021-9673
VL - 732
IS - 1
SP - 111
EP - 117
PB - Elsevier
CY - Amsterdam
AN - OPUS4-11347
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Decker, R.
A1 - Holländer, A.
T1 - Derivatization of Double Bonds investigated by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry
PY - 1997
SN - 0951-4198
SN - 1097-0231
VL - 11
SP - 914
EP - 918
PB - Wiley
CY - Chichester
AN - OPUS4-11097
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wettmarshausen, Sascha
A1 - Friedrich, Jörg Florian
A1 - Meyer-Plath, Asmus
A1 - Kalinka, Gerhard
A1 - Hidde, Gundula
A1 - Weidner, Steffen
T1 - Coating of carbon fibers with adhesion-promoting thin poly(acrylic acid) and poly(hydroxyethylmethacrylate) layers using electrospray ionization
N2 - Thin coatings of poly(acrylic acid) (PAA) and poly(hydroxyethylmethacrylate) (PHEMA) were deposited onto carbon fibers by means of the electrospray ionization (ESI) technique in ambient air. These high-molecular weight polymer layers were used as adhesion promoters in carbon fiberepoxy resin composites. Within the ESI process, the carbon fibers were completely enwrapped with polymer in the upper 10 plies of a carbon fiber roving. As identified with scanning electron microscopy also shadowed fibers in a bundle as well as backsides of fiber rovings were pinhole-free coated with polymers (electrophoretic effect'). Under the conditions used, the layers have a granular structure. Residual solvent was absent in the deposit. PAA and PHEMA films did not show any changes in composition and structure in comparison with the original polymers as analyzed by X-ray photo-electron spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Single-fiber pullout tests of coated fibers embedded in epoxy resin showed significantly increased interfacial shear strength. It is assumed that chemical bonds between carbon fiber poly(acrylic acid) and epoxy resin contribute significantly to the improved interactions.
KW - Adhesion promotion
KW - Thin polymer layers
KW - Electrospray ionization (ESI)
KW - Carbon fiberepoxy resin laminates
KW - Layer topography
PY - 2015
DO - https://doi.org/10.1080/01694243.2015.1040980
SN - 0169-4243
SN - 1568-5616
VL - 29
IS - 15
SP - 1628
EP - 1650
PB - VNU Science Press
CY - Utrecht
AN - OPUS4-34564
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Friedrich, Jörg Florian
A1 - Krüger, Ralph-Peter
A1 - Schulz, Günter
A1 - Much, Helmut
T1 - Liquid Adsorption Chromatography near Critical Conditions of Adsorption coupled with Matrix-assisted Laser/Ionization Mass Spectrometry
T2 - 47th ASMS Conference on Mass Spectrometry and Allied Topics
CY - Dallas, TX, USA
DA - 1999-06-13
PY - 1999
CY - Dallas, Tex
AN - OPUS4-2165
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Friedrich, Jörg Florian
A1 - Schulz, Eckhard
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
T1 - Verbesserungen der mechanischen Festigkeiten von Faser-Polymer-Verbundwerkstoffen durch Vorbehandlung der Fasern im Niederdruckplasma
T2 - Vortragsbände des 8. Internationalen Techtextil-Symposiums 1997
CY - Frankfurt am Main, Deutschland
DA - 1997-05-12
PY - 1997
VL - 8
SP - 1(?)
EP - 16(?)
PB - Messe Frankfurt
CY - Frankfurt am Main
AN - OPUS4-7287
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Sample spot heterogeneity investigated by MALDI-imaging mass spectrometry
T2 - 18th International Mass Spectrometry Conference
CY - Bremen, Germany
DA - 2009-08-30
PY - 2009
AN - OPUS4-19375
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Koshkina, Olga
A1 - Lang, Thomas
A1 - Thiermann, R.
A1 - Docter, D.
A1 - Stauber, R.H.
A1 - Secker, C.
A1 - Schlaad, H.
A1 - Weidner, Steffen
A1 - Mohr, B.
A1 - Maskos, M.
A1 - Bertin, Annabelle
T1 - Temperature-triggered protein adsorption on polymer-coated nanoparticles in serum
N2 - The protein corona, which forms on the nanoparticle's surface in most biological media, determines the nanoparticles physicochemical characteristics. The formation of the protein corona has a significant impact on the biodistribution and clearance of nanoparticles in vivo. Therefore, the ability to influence the formation of the protein corona is essential to most biomedical applications, including drug delivery and imaging. In this study, we investigate the protein adsorption on nanoparticles with a hydrodynamic radius of 30 nm and a coating of thermoresponsive poly(2-isopropyl-2-oxazoline) in serum. Using multiangle dynamic light scattering (DLS) we demonstrate that heating of the nanoparticles above their phase separation temperature induces the formation of agglomerates, with a hydrodynamic radius of 1 µm. In serum, noticeably stronger agglomeration occurs at lower temperatures compared to serum-free conditions. Cryogenic transmission electron microscopy (cryo-TEM) revealed a high packing density of agglomerates when serum was not present. In contrast, in the presence of serum, agglomerated nanoparticles were loosely packed, indicating that proteins are intercalated between them. Moreover, an increase in protein content is observed upon heating, confirming that protein adsorption is induced by the alteration of the surface during phase separation. After cooling and switching the surface back, most of the agglomerates were dissolved and the main fraction returned to the original size of approximately 30 nm as shown by asymmetrical flow-field flow fractionation (AF-FFF) and DLS. Furthermore, the amounts of adsorbed proteins are similar before and after heating the nanoparticles to above their phase-separation temperature. Overall, our results demonstrate that the thermoresponsivity of the polymer coating enables turning the corona formation on nanoparticles on and off in situ. As the local heating of body areas can be easily done in vivo, the thermoresponsive coating could potentially be used to induce the agglomeration of nanoparticles and proteins and the accumulation of nanoparticles in a targeted body region.
PY - 2015
DO - https://doi.org/10.1021/acs.langmuir.5b00537
SN - 0743-7463
SN - 1520-5827
VL - 31
IS - 32
SP - 8873
EP - 8881
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-34163
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gabriel, Stefan
A1 - Steinhoff, R.F.
A1 - Pabst, M.
A1 - Schwarzinger, C.
A1 - Zenobi, R.
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Improved analysis of ultra-high molecular mass polystyrenes in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using DCTB matrix and caesium salts
N2 - Rationale
The ionization of polystyrenes in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is typically achieved by the use of silver salts. Since silver salts can cause severe problems, such as cluster formation, fragmentation of polymer chains and end group cleavage, their substitution by alkali salts is highly desirable.
Methods
The influence of various cations (Ag+, Cs+ and Rb+) on the MALDI process of polystyrene (PS) mixtures and high mass polystyrenes was examined. The sample preparation was kept as straightforward as possible. Consequently, no recrystallization or other cleaning procedures were applied.
Results
The investigation of a polystyrene mixture showed that higher molecular polystyrenes could be more easily ionized using caesium, rather than rubidium or silver salts. In combination with the use of DCTB as matrix a high-mass polymer analysis could be achieved, which was demonstrated by the detection of a 1.1 MDa PS.
Conclusions
A fast, simple and robust MALDI sample preparation method for the analysis of ultra-high molecular weight polystyrenes based on the use of DCTB and caesium salts has been presented. The suitability of the presented method has been validated by using different mass spectrometers and detectors.
KW - MALDI
KW - Mega-dalton
KW - Ionization
KW - Caesium
KW - Polystyrene
KW - DCTB
PY - 2015
UR - http://onlinelibrary.wiley.com/doi/10.1002/rcm.7197/full
DO - https://doi.org/10.1002/rcm.7197
SN - 0951-4198
SN - 1097-0231
VL - 29
IS - 11
SP - 1039
EP - 1046
PB - Wiley
CY - Chichester
AN - OPUS4-33191
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Identification of End Group Heterogeneity of Modified Polyamide 6.6 utilizing Two-Dimensional Chromatography/MALDI-MS
T2 - 51st ASMS Conference
CY - Montreal, Canada
DA - 2003-06-08
PY - 2003
AN - OPUS4-4655
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Maltsev, Sergey
A1 - Sauerland, V.
A1 - Rinken, M.
T1 - A novel software tool for copolymer characterization by coupling of liquid chromatography with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
N2 - The results of copolymer characterization by coupling of chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) techniques and subsequent calculation of copolymer composition using a novel software tool MassChrom2D are presented. For high-resolution mass analysis copolymer samples were fractionated by means of liquid adsorption chromatography (LAC). These fractions were investigated off-line by MALDI-TOF MS. Various mono-n-butyl ethers of polyethylene oxide-polypropylene oxide copolymers (PEO-co-PPO) were investigated. As well as the copolymer composition presented in two-dimensional plots, the applied approach can give additional hints on specific structure-dependent separation conditions in chromatography.
KW - Copolymeranalytik
KW - MALDI
KW - Software
KW - MS/MS
KW - Kopplungsmethoden
PY - 2007
DO - https://doi.org/10.1002/rcm.3146
SN - 0951-4198
SN - 1097-0231
VL - 21
IS - 16
SP - 2750
EP - 2758
PB - Wiley
CY - Chichester
AN - OPUS4-17723
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Koprinarov, Ivaylo
A1 - Kühn, Gerhard
A1 - Weidner, Steffen
A1 - Vogel, Lydia
ED - Mittal, K.
T1 - Plasma Pretreatment of Polymer Surfaces - Relevance to Adhesion of Metals
T2 - 5th Symposium on Metallized Plastics ; 6th Symposium on Metallized Plastics
CY - Los Angeles, CA, USA
DA - 1996-05-05
PY - 1998
SN - 90-6764-290-8
SP - 271
EP - 293
PB - VSP
CY - Utrecht
AN - OPUS4-6987
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
T1 - Determination of critical conditions of adsorption for chromatography of polymers
N2 - Liquid chromatography (LC) at critical conditions of adsorption was used to separate various poly(ethylene oxides), poly(propylene oxides) and their copolymers. For the first time, the determination of the critical conditions by means of Ultra Performance Liquid Chromatography (UPLC) coupled to Electrospray Ionization Time-of-flight Mass Spectrometry (ESI-TOF MS) is reported. In contrast to established, mostly laborious routines to find suitable chromatographic separation conditions, this coupling enables a very fast adjustment of parameters. Similar to LC Matrix-assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (LC/MALDI MS) coupling, a two-dimensional analysis of homo- and copolymers regarding its functionality type and molecular weight distribution, as well as copolymer composition, can be performed simultaneously. Furthermore, there is no need for using polymer standards for the determination of critical conditions or Size Exclusion Chromatography calibration.
KW - Polymere
KW - UPLC
KW - ESI-Massenspektrometrie
KW - Kopplung
PY - 2009
DO - https://doi.org/10.1021/ac8019784
SN - 0003-2700
SN - 1520-6882
VL - 81
IS - 1
SP - 282
EP - 287
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-19619
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kühn, Gerhard
A1 - Weidner, Steffen
A1 - Decker, Renate
A1 - Ghode, Archana
A1 - Friedrich, Jörg Florian
T1 - Selective surface functionalization of polyolefins by plasma treatment followed by chemical reduction
N2 - Polymer surfaces can be finished with functional groups upon exposure to a plasma. Species of the plasma gas are attached at surface carbon atoms, forming functional groups of different composition. To produce a modified polymer surface with a high density and homogeneity of hydroxyl groups only, the oxygen-plasma-formed oxygen functional groups were chemically reduced by diborane and LiAlH4 with yields of 10 to 11 OH groups per 100 carbon atoms in the 3 to 5 nm near-surface layer as detected by X-ray photoelectron spectroscopy (XPS). The identification of hydroxyl groups was performed by means of attenuated total reflectanceFourier transform infrared spectroscopy and XPS.
KW - Attenuated total reflectance-Fourier transorm infrared spectroscopy
KW - Chemical reduction of functional groups
KW - Plasma modification
KW - X-ray photoelectron spectroscopy
PY - 1999
DO - https://doi.org/10.1016/S0257-8972(99)00232-7
SN - 0257-8972
VL - 116-119
SP - 796
EP - 801
PB - Elsevier Science
CY - Lausanne
AN - OPUS4-6983
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Krüger, Ralph-Peter
A1 - Falkenhagen, Jana
A1 - Much, Helmut
A1 - Schulz, Günter
A1 - Weidner, Steffen
T1 - Charakterisierung von synthetischen Polymeren durch Kopplung flüssigchromato-graphischer Trennmethoden mit der MALDI-TOF-Massenspektrometrie
T2 - 1. Berliner Werkstofftag
CY - Berlin, Deutschland
DA - 1999-09-16
PY - 1999
AN - OPUS4-2242
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.R.
A1 - Yashiro, T.
A1 - Weidner, Steffen
T1 - Isomerization-free polycondensations of maleic anhydride with alpha,omega-alkanediols
KW - Polymerisation
KW - Polykondensation
KW - MALDI Massenspektrometrie
PY - 2009
DO - https://doi.org/10.1021/ma9009356
SN - 0024-9297
SN - 1520-5835
VL - 42
IS - 17
SP - 6433
EP - 6439
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-20930
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Determination of molecular mass and molecular mass distribution of polymers by matrixassisted laser desorption/ionization - time of fightmass spectrometry (MALDI TOF MS)
T2 - ISO TC 61/SC 5 Meeting
CY - Yokohama, Japan
DA - 2006-09-18
PY - 2006
AN - OPUS4-13822
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Holländer, A.
A1 - Kühn, Gerhard
T1 - Matrix-assisted Laser Desorption/Ionization Mass Spectrometry of C36- Alkane degradated by Vacuum Ultraviolet Radiation
PY - 1997
SN - 0951-4198
SN - 1097-0231
VL - 11
SP - 447
EP - 450
PB - Wiley
CY - Chichester
AN - OPUS4-11095
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Hyphenated coupling methods for polymer characterization and identification
T2 - Dutch Polymer Workshop
CY - Jena, Germany
DA - 2013-12-09
PY - 2013
AN - OPUS4-30268
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Trimpin, S.
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - McEwen, C.N.
T1 - Fractionation and Solvent-Free MALDI-MS Analysis of Polymers Using Liquid Adsorption Chromatography at Critical Conditions in Combination with a Multisample On-Target Homogenization/Transfer Sample Preparation Method
N2 - A solvent-free homogenization/transfer matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) method is described for the preparation and precise transfer of up to 100 samples simultaneously on a single MALDI plate. This method is demonstrated using a poly(ethylene oxide) (PEO) mixture consisting of different molecular weights (500-6000) and end groups (PEO, dimethoxy-PEO, monomethoxy monomethacrylate-PEO, and dimethacrylate-PEO) that was fractionated using liquid adsorption chromatography at critical conditions. Off-line fractionation is performed prior to the on-target homogenization/transfer solvent-free sample preparation and MALDI mass analysis. The miniaturization of the solvent-free MALDI approach allowed analysis of less than 2 g per PEO component per fraction corresponding to ~200 pmol for PEO 6000. The amounts of polymer sample used for LC separation and the quality of the MS results are equivalent to the "dry spray" method; however, three times more fractions were collected and analyzed with the newly developed hyphenated approach. The off-line method eliminates optimization of, for example, spray conditions or spreading of organic solvents on the MALDI plate that occurs with droplet deposition methods. The widespread applications of MALDI make this solvent-free, multisample method particularly important as it expands the capabilities for obtaining mass measurements with great efficiencies in areas with increased sample numbers. In addition, the solvent-free method is well suited for automated MALDI analysis as it virtually eliminates the "dead-spot" phenomenon.
PY - 2007
DO - https://doi.org/10.1021/ac070986w
SN - 0003-2700
SN - 1520-6882
VL - 79
IS - 19
SP - 7565
EP - 7570
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-17737
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
T1 - Detection limits of matrix-assisted laser desorption/ionisation mass spectrometry coupled to chromatography - a new application of solvent-free sample preparation
N2 - The detection limits of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) by semi-online coupling with chromatography were investigated using various mixtures of polyethylene oxides (PEOs) with different end groups. In contrast to the common dried-droplet sample preparation technique, which results in an inhomogeneous sample-to-matrix ratio within the MALDI spot, the used coupling technique offers a very high reproducibility combined with surpassing sensitivity of a few femtograms over a broad range of sample-to-matrix ratios. These results are in correlation with the results of the recently established solvent-free MALDI-TOFMS method utilising the grinding approach and are also of assistance towards the more theoretical aspect of MALDI that suggests that there is no necessity for an analyte incorporation into a matrix crystal for excellent matrix-assistance.
PY - 2005
DO - https://doi.org/10.1002/rcm.2256
SN - 0951-4198
SN - 1097-0231
VL - 19
IS - 24
SP - 3724
EP - 3730
PB - Wiley
CY - Chichester
AN - OPUS4-11859
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Giebler, Rainer
A1 - Koprinarov, Ivaylo
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
ED - Mittal, K. L.
T1 - Significance of interfacial redox reactions and formation of metal-organic complexes for the adhesion of metals on pristine and plasma-treated polymers
KW - Oxygen low-pressure plasma treatment of polymers
KW - Metal-polymer interactions
KW - Peel strength
PY - 2000
SN - 90-6764-327-0
VL - 2
SP - 137
EP - 171
PB - VSP
CY - Utrecht
AN - OPUS4-6979
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Falkenhagen, Jana
A1 - Krüger, Ralph-Peter
A1 - Much, Helmut
A1 - Schulz, Günter
A1 - Weidner, Steffen
ED - Grellmann, W.
T1 - Characterization and identification of new polymer structures by optimization and coupling of HPLC and MALDI-TOF-MS
T2 - Polymerwerkstoffe 2000
CY - Halle (Saale), Germany
DA - 2000-09-25
PY - 2000
SN - 3-86010-605-8
PB - Martin-Luther-Univ.
CY - Halle
AN - OPUS4-2250
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Wolff, D.
A1 - Springer, J.
T1 - Influence of Spacer Variation on Phase Behaviour of Liquid-Crystalline Copolymethacrylates containing Cholesterol and S-(-)-4,4'-chloropropionyl-oxybiphenyl
PY - 1997
SN - 0267-8292
SN - 1366-5855
VL - 22
IS - 2
SP - 193
EP - 201
PB - Taylor & Francis
CY - London
AN - OPUS4-11096
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MassChrom2D zur Bestimmung der Zusammensetzung von Copolymeren aus MALDI und LC Daten
T2 - 16. Kolloquium MALDI und Synthetische Polymere
CY - Berlin, Germany
DA - 2012-05-08
PY - 2012
AN - OPUS4-26135
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Trimpin, S.
T1 - Mass Spectrometry of Synthetic Polymers
KW - Mass Spectrometry
KW - Polymers
KW - Application
PY - 2008
DO - https://doi.org/10.1021/ac8006413
SN - 0003-2700
SN - 1520-6882
VL - 80
IS - 12
SP - 4349
EP - 4361
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-17718
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Scholz, Philipp
A1 - Ulbricht, Alexander
A1 - Joshi, Y.
A1 - Gollwitzer, Christian
A1 - Weidner, Steffen
T1 - Microstructure of polymer-imprinted metal–organic frameworks determined by absorption edge tomography
N2 - Mechanochemically synthesized metal–organic Framework material HKUST-1 in combination with acrylonitrile butadiene styrene polymer was used to form a polymer metal–organic framework composite material by a simple extruder.
This composite filament was used for 3D printing. Xray diffraction measurements were used to prove the homogeneous distribution of the metal–organic framework in the polymer on a centimeter scale, whereas X-ray Absorption Edge Tomography using a synchrotron radiation source was able to evaluate the 3D distribution of the metal–organic framework material both in the filament and the resultant printed sample with a resolution of a few lm. Our very first data indicate that, apart from a few clusters having significantly higher Cu concentration, HKUST-1 is distributed homogeneously down to the 100 lm length scale in both polymer bulk materials in the form of clusters with a size of a few lm. Absorption Edge Tomography in combination with data fusion also allows for the calculation of the metal–organic framework amount located on the external polymer surface.
KW - MOF
KW - Polymer
KW - AET
PY - 2019
DO - https://doi.org/10.3139/146.111817
SN - 1862-5282
SP - 1
EP - 10
PB - Carl Hanser Verlag
AN - OPUS4-49483
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Liquid Adsorption Chromatography near Critical Conditions of Adsorption coupled with Matrix-assisted Laser Desorption / ionization Mass Spectrometry
T2 - 47th Conference of The American Society of Mass Spectrometry
CY - Dallas, TX, USA
DA - 1999-06-11
PY - 1999
AN - OPUS4-2240
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Zweidimensionale Charakterisierung von PA 6.6 durch Kopplung von LAC und MALDI-MS
T2 - 7. Kolloquium "MALDI und synthetische Polymere"
CY - Berlin, Germany
DA - 2003-05-13
PY - 2003
AN - OPUS4-3094
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CHAP
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
ED - Li, L.
T1 - LC-MALDI MS for polymer characterization
KW - Mass spectrometry
KW - Polymers
PY - 2010
SN - 978-0-471-77579-9
N1 - Serientitel: Chemical analysis: a series of monographs on analytical chemistry and its applications – Series title: Chemical analysis: a series of monographs on analytical chemistry and its applications
VL - 175
IS - Chapter 11
SP - 247
EP - 265
PB - John Wiley & Sons
AN - OPUS4-26406
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Cyclic poly(lactide)s via the ROPPOC method catalyzed by alkyl- or aryltin chlorides
N2 - A comparison of tributyltin chloride, dibutyltin dichloride,and butyltin trichloride as catalysts of ring-opening polymerizations(ROPs) of l-lactides at 160°C in bulk reveals increasing reactivity in the above order, but only the least reactive catalysts, Bu3SnCl, yield a uniform reaction product, namely cyclic poly(L-lactide)s with weight average molecular weights (Mw ́s) in the range of 40,000–80,000. A comparison of dimethyltin , dibutyltin , and diphenyltin dichlorides resulted in the following order of reactivity: Me2SnCl2 189 °C was monitored by means of DSC measurements and characterized in selected cases by SAXS measurements. It was confirmed that the formation of HTm crystallites involves a significant growth of the thickness of the lamellar crystallites along with smoothing of their surface. Annealing at 170 °C for 1 d or longer causes thermal degradation with lowering of the molecular weights, a gradual transition of cyclic into linear chains and a moderate decrease of lamellar thickness. An unexpected result revealed by MALDI TOF mass spectrometry is a partial reorganization of the molecular weight distribution driven by a gain of crystallization enthalpy.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystallization
KW - Annealing
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521062
DO - https://doi.org/10.1039/d0ra10012a
VL - 11
IS - 5
SP - 2872
EP - 2883
PB - Royal Society of Chemistry
AN - OPUS4-52106
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Polymerization of L-lactide with SnCl2: A Low Toxic and Eco-friendly Catalyst
N2 - Polymerizations of L-lactide catalyzed either by neat SnCl2 or by SnCl2 + difunctional cocatalysts were conducted in bulk at 180, 160 and 140 °C with variation of the Lac/Cat ratio and time. With neat SnCl2 poly(L-lactide) having weight average molecular weights (uncorrected Mw’s) up to 190 000 g mol−1 were obtained mainly consisting of linear chains. Addition of salicylic acid or 1,1-bisphenol yielded a higher fraction of cyclic polylactides but lower molecular weights. Furthermore, SnCl2 was compared with Bu2SnCl2 and various other metal chlorides and the best results were obtained with SnCl2. With ethyl L-lactate as initiator SnCl2-catalyzed ROPs were performed at 120 °C and the lac/initiator ratio was varied. All these experiments were conducted under conditions allowing for comparison with ROPs catalyzed with neat Sn(II)-2-ethyhexanoate. Such a comparison was also performed with ε-caprolactone as monomer.
KW - Catalyst
KW - Polylactide
KW - MALDI-TOF MS
KW - Polycondensation
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520517
DO - https://doi.org/10.1007/s10924-020-02042-w
SN - 1566-2543
SP - 1
EP - 13
PB - Springer Nature
AN - OPUS4-52051
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - High molecular weight poly(l-lactide) via ring-opening polymerization with bismuth subsalicylate-The role of cocatalysts
N2 - The catalytic potential of bismuth subsalicylate (BiSub), a commercial drug, for ring-opening polymerization (ROP) of L-lactide was explored by variation of co-catalyst and polymerization time. Various monofunctional phenols or carboxylic acids, aromatic ortho-hydroxy acids and diphenols were examined as potential co-catalysts. 2,2´-Dihydroxybiphenyl proved to be the most successful co-catalyst yielding weight average molecular weights (uncorrected Mw values up to 185 000) after optimization of reaction time and temperature. Prolonged heating (>1-2h) depending on catalyst concentration) caused thermal degradation. In polymerization experiments with various commercial Bi(III) salts a better alternative to BiSub was not found. By means of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry a couple of unusual and unexpected transesterification reactions were discovered. Finally, the effectiveness of several antioxidants and potential catalyst poisons was explored, and triphenylphosphine was found to be an effective catalyst poison.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring-opening polymerization
KW - Bismuth
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-519513
DO - https://doi.org/10.1002/app.50394
SN - 0021-8995
VL - 138
IS - 19
SP - 50394
PB - Wiley
AN - OPUS4-51951
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - ROP of L-lactide and ε-caprolactone catalyzed by tin(ii) and tin(iv) acetates–switching from COOH terminated linear chains to cycles
N2 - The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations of L-lactide conducted in bulk at 160 or 130C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied and linear chains having one acetate and one carboxyl end group almost free of cyclics were obtained. Higher monomer/catalyst ratios and lower temperatures favored formation of cycles that reached weight average molecular weights (Mw's) between 100,000 and 2,500,000. SnAc4 yielded mixtures of cycles and linear species under all reaction conditions. Dibutyltin- and dioctyl tin bis-acetate yielded cyclic polylactides under most reaction conditions with Mw's in the range of 20,000–80,000. Ring-opening polymerizations performed with ε-caprolactone showed similar trends, but the formation of COOH-terminated linear chains was significantly more favored compared to analogous experiments with lactide. The reactivity of the acetate catalysts decreased in the following order: SnAc2> SnAc4>Bu2SnAc2 Oct2SnAc2.
KW - Catalyst
KW - MALDI-TOF MS
KW - Ring-opening polymerization
KW - Tin acetates
KW - Polylactide
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520831
DO - https://doi.org/10.1002/pol.20200866
SP - 1
EP - 12
PB - Wiley Online Library
AN - OPUS4-52083
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H. R.
A1 - Scheliga, F.
T1 - Ring-expansion copolymerization of L-lactide and glycolide
N2 - 1:1 Copolymerizations of glycolide (GL) and L-lactide (LA) is performed in bulk at 100°C and at 160°C with four cyclic tin catalysts. The resulting copolyesters are characterized by SEC measurements, 1H and 13C NMR spectroscopy and by MALDI TOF mass spectrometry. At 160°C and longer reaction time (22 h) nearly complete conversion of both monomers is achieved, and cyclic copolymers with nearly random sequences are formed. At shorter times (0.5-3.0 h, depending on catalyst) the conversion of LA is incomplete, and only cyclics having even numbers of lactyl units are obtained. At 100°C at 22 h again cycles mainly consisting of even numbered lactyl units are formed, but with even and odd numbers of glycolyl units. Copolymerization of lactide at 160°C with small amounts of GL show that formation of high Tm crystallites (Tm > 190°C) is hindered even when only > 2% of GL is added. For polyglycolide containing a smaller amount of lactide complete solubility in hexafluoroisopropanol is only observed around and above 20 mol% of lactide.
KW - Ring-expansion polymerization
KW - Copolymerization
KW - MALDI-TOF MS
KW - L-lactide
KW - Glycolide
KW - Crystallization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520270
DO - https://doi.org/10.1002/macp.202000307
SN - 1022-1352
VL - 22
IS - 3
SP - 307
PB - WileyVCH
AN - OPUS4-52027
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Reply to the comment on “synthesis of cyclic polymers and flaws of the Jacobson-Stockmayer theory” by R. Szymanski
N2 - In a recent publication the authors have presented theoretical and experimental results indicating that the Jacobson–Stockmayer (JS) theory does not provide a correct description of reversible polycondensations for all polymers and for high conversions (e.g. polycondensation in bulk). In this context reversibility means that all condensation step whether resulting in chain growth or in cyclization are reversible and thus, part of an equilibrium. The first two sections of that paper were focused on the demonstration that small, and above all, large cycles can be formed by end-to-end (ete) cyclization in reversible like in irreversible polycondensations. A significant contribution of ete-cyclization to the course of reversible polycondensations was denied by J + S apparently as a contribution to Florýs dogma, that the end groups of long polymer chains will never meet.
KW - Polylactide
KW - MALDI-TOF MS
KW - Jacobsen-Stockmayer theory
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513985
DO - https://doi.org/10.1039/D0PY01118E
VL - 11
IS - 38
SP - 6226
EP - 6228
PB - Royal Society of Chemistry
AN - OPUS4-51398
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H.
T1 - Cyclic polyglycolides via ring-expansion polymerization with cyclic tin catalysts
N2 - Glycolide was polymerized in bulk with two cyclic catalysts − 2,2-dibutyl-2-stanna-1,3-dithiolane (DSTL) and 2-stanna-1,3-dioxa-4,5,6,7-dibenzepane (SnBiph). The monomer/initiator ratio, temperature (140 – 180 °C) and time (1–––4 days) were varied. The MALDI TOF mass spectra exclusively displayed peaks of cyclic polyglycolide (PGA) and revealed an unusual “saw-tooth pattern” in the mass range below m/z 2 500 suggesting formation of extended ring crystallites. The DSC measurements indicated increasing crystallinity with higher temperature and longer time, and after annealing for 4 d at 160 °C a hitherto unknown and unexpected glass transition was found in the temperature range of 170–185 °C. Linear PGAs prepared by means of metal alkoxides under identical conditions did not show the afore-mentioned features of the cyclic PGAs, neither in the mass spectra nor in the DSC measurements. All PGAs were also characterized by SAXS measurements, which revealed relatively small L-values suggesting formation of thin crystallites in all cases with little influence of the reaction conditions.
KW - Polyglycolide
KW - MALDI-TOF MS
KW - Ring-expansion polymerization
KW - Crystals
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595541
DO - https://doi.org/10.1016/j.eurpolymj.2024.112811
SN - 0014-3057
VL - 207
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-59554
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Polycondensation of poly(L-lactide) alkyl esters combined with disproportionation and symproportionation of the chain lengths
N2 - Ring-opening polymerizations (ROPs) of l-lactide (LA) were performed with ethyl l-lactate or 11-bromoundecanol as initiators (In) and tin(II) ethyl hexanoate (SnOct2) as catalyst (Cat) using four different LA/In ratios (20/1, 40/1, 60/1, and 100/1). One series of ROPs was conducted in bulk at 120 °C, yielding PLAs with low dispersities (Ð ~ 1.2–1.4), and a second series was conducted in bulk at 160 °C, yielding higher dispersities (Ð ~ 1.3–1.9). Samples from both series were annealed for 1 or 14 days at 140 °C in the presence of SnOct2. Both polycondensation and disproportionation reactions occurred, so that all four samples tended to form the same type of molar mass distribution below 10,000 Da, regardless of their initially different number average molar masses (Mn). Both initiators gave nearly identical results. The thermodynamic control of all reversible transesterification processes favored the formation of crystallites composed of chains with a Mn around 3500–3700, corresponding to a crystal thickness of 10–13 nm.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600081
DO - https://doi.org/10.1002/pol.20240118
SN - 2642-4150
SP - 1
EP - 12
PB - Wiley
AN - OPUS4-60008
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - Syntheses of high molecular mass polyglycolides via ring-opening polymerization with simultaneous polycondensation (ROPPOC) by means of tin and zinc catalysts
N2 - Glycolide was polymerized in bulk by means of four different ROPPOC catalysts: tin(II) 2-ethylhexanoate (SnOct2), dibutyltin bis(pentafluoro-phenoxide) (BuSnOPF),zinc biscaproate (ZnCap), and zinc bis(pentafluoro-phenyl sulfide) (ZnSPF). The temperature was varied between 110 and 180°C and the time between 3 h and 7 days. For the few polyglycolides (PGAs) that were soluble extremely high molecular masses were obtained. The MALDI TOF mass spectra had all a low signal-to-noise ration and displayed the peaks of cyclic PGAs with a“saw-tooth pattern ”indicating formation of extended-ring crystallites in the mass range below m/z 2500. The shape of DSC curves varied considerably with catalyst and reaction conditions, whereas the long-distance values measured by SAXS were small and varied little with the polymeriza-tion conditions.
KW - MALDI TOF MS
KW - Polyglycolide
KW - Crystalinity
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598221
DO - https://doi.org/10.1002/pat.6365
VL - 35
IS - 4
SP - 1
EP - 10
PB - John Wiley & Sons Ltd.
AN - OPUS4-59822
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
T1 - Low Molar Mass Cyclic Poly(L-lactide)s: Separate Transesterification Reactions of Cycles and Linear Chains in the Solid State
N2 - L-Lactide (LA) was polymerized with neat tin(II) 2-ethylhexanoate (SnOct2) in toluene at 115 °C at low concentration with variation of the LA/Cat ratio. Cyclic polylactides (cPLAs) with number average molecular weights (Mn) between 7 000 and 17 000 were obtained. MALDI-TOF mass spectrometry also revealed the formation of a few percent of linear chains. Crystalline cPLAs with Mn around 9 000 and 14 000 were annealed at 140 °C in the presence of ScOct2 or dibutyl-2-stanna-1,3-dithiolane (DSTL). Simultaneously, crystallites of extended linear chains and crystallites of extended cycles were formed regardless of the catalyst, indicating that transesterification reaction proceeded different for linear chains and for cycles, governed by thermodynamic control. The formation of extended chain crystallites with low dispersity indicates the existence of symproportionation of short and long chains. A complementary experiment was carried out with a PLA ethyl ester composed mainly of linear chains with a small fraction of cycles
KW - Polylactide
KW - MALDI-TOF MS
KW - Annealing
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-606228
DO - https://doi.org/10.1039/D4SM00567H
SN - 1744-6848
SP - 1
EP - 12
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-60622
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dalgic, Mete-Sungur
A1 - Weidner, Steffen
T1 - Solvent-free sample preparation for matrix-assisted laserdesorption/ionization time-of-flight mass spectrometry ofpolymer blends
N2 - Solvent-free sample preparation offers some advantages over solvent-based techniques, such as improved accuracy, reproducibility and sensitivity, for matrix-assisted laser desorption/ionization (MALDI) analysis. However, little or no information is available on the application of solvent-free techniques for the MALDI analysis of polymer blends. Solvent-free sample preparation by ball milling was applied with varying sample-to-matrix ratios for MALDI time-of-flight mass spectrometry analysis of various polymers, including polystyrenes, poly(methyl methacrylate)s and poly(ethylene glycol)s. The peak intensity ratios were compared with those obtained after using the conventional dried droplet sample preparation method. In addition, solvent-assisted milling was also applied to improve sample homogeneities.
Depending on the sample preparation method used, different peak intensity ratios were found, showing varying degrees of suppression of the signal intensities of higher mass polymers. Ball milling for up to 30 min was required to achieve constant intensity ratios indicating homogeneous mixtures. The use of wet-assisted grinding to improve the homogeneity of the blends was found to be disadvantageous as it caused partial degradation and mass-dependent segregation of the polymers in the vials.The results clearly show that solvent-free sample preparation must be carefully considered when applied to synthetic polymer blends, as it may cause additional problems with regard to homogeneity and stability of the blends.
KW - MALDI TOF MS
KW - Sample preparation
KW - Polymer blends
KW - Solvent-free
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598570
DO - https://doi.org/10.1002/rcm.9756
SN - 0951-4198
VL - 38
IS - 12
SP - 1
EP - 9
PB - Wiley online library
AN - OPUS4-59857
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H.
T1 - Transformation of poly(L-lactide) crystals composed of linear chains into crystals composed of cycles
N2 - A poly(L-lactide) with a trifluoroethyl ester end group and an average degree of polymerization (DP) of 50 was synthesized by ROP of L-lactide initiated with trifluoroethanol. Small-angle X-ray scattering (SAXS) in combination with differential scanning calorimetry (DSC) measurements revealed an average crystal thickness of 13 nm, corresponding to 45 repeat units. This suggests that most crystallites were formed by extended PLA chains, and both flat surfaces were covered by CF3 groups. The crystalline PLAs were annealed at 140 or 160 °C in the presence of two catalysts: tin(II) 2-ethylhexanoate, (SnOct2) or dibutyltin bis(pentafluorophenoxide) (BuSnPhF). The chemical reactions, such as polycondensation and cyclization, proceeded in the solid state and were monitored by matrix-assisted laser desorption/ionization time-offlight (MALDI TOF) mass spectrometry and gel permeation chromatography (GPC) measurements. Under optimal conditions a large fraction of linear chains was transformed into crystallites composed of extended cycles. Additionally, MALDI TOF MS analysis of GPC fractions from samples annealed for 28 or 42 days detected chain elongation of the linear species up to a factor of 20.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
KW - Transesterification
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597250
DO - https://doi.org/10.1039/D3PY01370G
SN - 1759-9954
VL - 15
IS - 12
SP - 1173
EP - 1181
PB - Royal Society for Chemistry
AN - OPUS4-59725
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H. R.
T1 - Matrix-assisted laser desorption/ionization behavior of neat linear and cyclic poly(L-lactide)s and their blends
N2 - Numerous new tin catalysts that enable the synthesis of cyclic polylactides with broad variation in their molecular mass were recently developed. The abundance of cyclics in matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra is, however, frequently reported to greatly exceed that of linears. Thus, the MALDI ionization behavior of various end-capped linear poly(L-lactide)s and one cyclic poly(L-lactide) was investigated and compared.
Neat compounds and various blends of cyclic and linear species were prepared and studied under identical conditions with regard to sample preparation and instrumental condition, except for the laser power. For this purpose, two different MALDI-TOF mass spectrometers were applied.
Our results reveal that cyclics indeed show a slightly better ionization in MALDI, although their ionization as a neat compound seems to be less effective than that of linear polylactides. The ionization of most linear polylactides investigated does not depend on the end group structure. However, linear polylactides containing 12-bromododecyl end groups reveal an unexpected saturation effect that is not caused by fragmentation of the polymer or the end group, or by electronic saturation of the detector digitizer. Furthermore, polylactides with a 2-bromoethyl end group did not show such a saturation effect.
An overestimation of cyclic species in MALDI-TOF mass spectra of poly(L-lactide)s must be considered, but the commonly assumed peak suppression of linear polymers in mixtures of both structures can be excluded.
KW - Polylactide
KW - MALDI-TOF MS
KW - Blends
KW - Ionization
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-504216
DO - https://doi.org/10.1002/rcm.8673
VL - 34
SP - e8673
PB - Wiley Online Libary
AN - OPUS4-50421
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yameen, B.
A1 - Zydziak, N.
A1 - Weidner, Steffen
A1 - Bruns, M.
A1 - Barner-Kowollik, C.
T1 - Conducting polymer/SWCNTs modular hybrid materials via Diels-Alder ligation
N2 - The development of a facile covalent strategy for the fabrication of organic conducting polymers (OCPs)/carbon nanotubes (CNTs) based molecular hybrid materials remains a challenge and is expected to address the detrimental intrinsic bundling issue of CNTs. In view of the pristine CNTs' ability to undergo Diels–Alder reactions with dienes, we report the synthesis of a novel poly(3-hexylthiophene) (P3HT) based organic conducting polymer (OCP) with terminal cyclopentadienyl (Cp) groups. The synthetic strategy employed is based on a combination of in situ end group functionalization via Grignard metathesis (GRIM) polymerization and a subsequent end group switching via reaction with nickelocene. Characterization data from Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDITOF MS) fully support the successful synthesis of monofunctional Cp-capped P3HT, which was found to be highly reactive toward dienophile end-capped polystyrene (PS). The Cp-capped P3HT was subsequently ligated to the surface of pristine single walled CNTs (SWCNTs). The resulting P3HT/SWCNTs molecular hybrid material was characterized using thermogravimetric analysis (TGA), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HRTEM). The data from TGA, EA, and XPS were used to quantitatively deduce the grafting density. P3HT/SWCNTs prepared with Cp capped P3HT was found to contain 2 times more P3HT than the reference sample, featuring a grafting density of 0.0510 chains·nm–2 and a periodicity of 1 P3HT chain per 748 carbon atoms of the SWCNTs. HRTEM revealed individual SWCNTs wrapped with P3HT whereas in the reference sample P3HT was adsorbed on the bundles of the SWCNTs. The results presented here provide a new avenue for designing novel materials based on CNTs and OCPs.
KW - Mass spectrometry
KW - Polymers
PY - 2013
DO - https://doi.org/10.1021/ma4004055
SN - 0024-9297
SN - 1520-5835
VL - 46
IS - 7
SP - 2606
EP - 2615
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-28575
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gabriel, Stefan
A1 - Pfeifer, Dietmar
A1 - Schwarzinger, C.
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric imaging of synthetic polymer sample spots prepared using ionic liquid matrices
N2 - RATIONALE
Polymer sample spots for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) prepared by the dried-droplet method often reveal ring formation accompanied by possible segregation of matrix and sample molecules as well as of the polymer homologs itself. Since the majority of sample spots are prepared by this simple and fast method, a matrix or sample preparation method that excludes such segregation has to be found.
METHODS
Three different ionic liquid matrices based on conventionally used aromatic compounds for MALDI-TOF MS were prepared. The formation of ionic liquids was proven by 1H NMR spectroscopy. MALDI-Imaging mass spectrometry was applied to monitor the homogeneity.
RESULTS
Our results show a superior sample spot homogeneity using ionic liquid matrices. Spots could be sampled several times without visible differences in the mass spectra. A frequently observed loss of matrix in the mass spectrometer vacuum was not observed. The necessary laser irradiance was reduced, which resulted in less polymer fragmentation.
CONCLUSIONS
Ionic liquid matrices can be used to overcome segregation, a typical drawback of conventional MALDI dried-droplet preparations. Homogeneous sample spots are easy to prepare, stable in the MS vacuum and, thereby, improve the reproducibility of MALDI.
PY - 2014
DO - https://doi.org/10.1002/rcm.6810
SN - 0951-4198
SN - 1097-0231
VL - 28
IS - 5
SP - 489
EP - 498
PB - Wiley
CY - Chichester
AN - OPUS4-30267
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
A1 - Scheliga, Felix
T1 - Cyclic poly(l-lactide) via ring-expansion polymerization by means of dibutyltin 4-tert-butylcatecholate
N2 - Five new catalysts are prepared from dibutyltin oxide and catechol (HCa),
2,3-dihydroxynaphthalene (NaCa), 4-tert-butyl catechol (BuCa), 4-cyano
catechol (CyCa), and 4-benzoyl catechol (BzCa), but only BuCa gives useful
results. When benzyl alcohol is used as an initiator, linear chains having
benzyl ester end groups are formed in a slow polymerization process. In
contrast to cyclic or noncyclic dibutyltin bisalkoxides, neat BuCa yields
cyclic poly(l-lactide)s via a fast ring-expansion polymerization. Under certain
conditions, a high-melting crystalline phase (Tm = 191 °C) is obtained.
At 160 °C and short reaction times even-numbered cycles are slightly
prevailing, but, surprisingly, at 120 °C, odd-numbered cycles are predominantly
formed. These results definitely prove that a ring-expansion mechanism
is operating.
KW - Lactides
KW - MALDI TOF MS
KW - Morphology
KW - Ring-opening polymerization
KW - Tin catalysts
PY - 2017
DO - https://doi.org/10.1002/macp.201700274
SN - 1521-3935
SN - 1022-1352
VL - 218
IS - 22
SP - 1700274, 1
EP - 1700274, 10
PB - Wiley VCH
CY - Weinheim
AN - OPUS4-43583
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.R.
A1 - Weidner, Steffen
T1 - Copolyesters of lactide, isosorbide, and terephthalic acid-biobased, biodegradable, high-Tg engineering plastics
N2 - Various copolyesters of lactide, isosorbide, and terephthalic acid are prepared by a two-step process performed in a 'one-pot' procedure, beginning with an isosorbide-initiated oligomerization of L-lactide followed by polycondensation with terephthaloyl chloride using SnCl2 as a catalyst for both steps. The SEC data show the formation of random copolyesters with high polydispersities as a consequence of the relatively high fraction of cyclics proved by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The glass-transition temperatures (89–180 °C) obey an almost linear trend with the molar composition. The thermostability decreases with increasing lactide content. The successful incorporation of phenyl phosphate results in copolyesters of lower inflammability.
KW - Biodegradability
KW - Cyclization
KW - Isosorbide
KW - Polycondensation
KW - Ring-opening polymerization
PY - 2013
DO - https://doi.org/10.1002/macp.201200612
SN - 1022-1352
SN - 1521-3935
VL - 214
IS - 6
SP - 726
EP - 733
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-28171
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
T1 - LC-MALDI-TOF imaging MS: a new approach in combining chromatography and mass spectrometry of copolymers
N2 - A new approach that utilizes MALDI-TOF imaging mass spectrometry as a new detector for polymer chromatography is presented. For the first time, the individual retention behavior of single structural units of polyethylene oxide (PEO)/polypropylene oxide (PPO) copolymers and changes of the copolymer composition could be monitored. Composition specific calibration curves could be easily obtained by displaying the copolymer ion intensity data. This approach provides completely new insights in the chromatographic principle of copolymer separation and could be used to easily modify and adapt conditions for separation. In combination with electrospray deposition, homogeneous sample/matrix traces of surprisingly high spatial resolution could be obtained.
KW - MALDI
KW - Massenspektrometrie
KW - Imaging
KW - Chromatographie
KW - Polymere
PY - 2011
DO - https://doi.org/10.1021/ac202380n
SN - 0003-2700
SN - 1520-6882
VL - 83
IS - 23
SP - 9153
EP - 9158
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-24974
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Weidner, Steffen
A1 - Geng, Sh.
A1 - Wigant, L.
A1 - Wöll, Ch.
A1 - Erdmann, J.
A1 - Gorsler, H.-V.
T1 - Characterization of plasma-modified organic surfaces by electron spectroscopy, SEIRA, and MALDI-TOF-MS
T2 - 6th European Conference on Applications of Surface and Interface Analysis
CY - Montreux, Switzerland
DA - 1995-10-09
PY - 1995
SP - TC 11
PB - Wiley
CY - Chichester
AN - OPUS4-7001
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Phasenverhalten Cholesterin enthaltender Seitengruppenpolymere
T2 - TU Berlin, AK Prof. Springer
CY - Berlin, Germany
DA - 1995-11-13
PY - 1995
AN - OPUS4-11275
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Cherbib, S.
A1 - Jlalia, I.
A1 - Chabbah, T.
A1 - Chatti, S.
A1 - Marestin, C.
A1 - Mercier, R.
A1 - Weidner, Steffen
A1 - Casabianca, H.
A1 - Jaffrezic-Renault, N.
A1 - Abderrazak, H.
T1 - Design of New Partially Bio-Based Polyguanamines for the Reversible Adsorption of Phenolic Molecules from Olive Mill Wastes
N2 - Olive mill wastewater produces a variety of potent antioxidants, including hydroxytyrosol, oleuropein, and tyrosol, that have been widely used in agriculture, pharmacy, and cosmetics. This study aims to design new poly(guanamine)s phases by polycondensation of modified triazine monomers with both petro-based and biosourced diamines, to act as stationary phases for the uptake of these phenolic molecules. Obtained polymers were characterized by NMR spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The adsorption results showed that the newly synthesized polymers can effectively uptake the less polar phenolic compounds, ferulic acid, and caffeic acid. The isosorbide-based polymer (P6) presented the highest sorption efficiency, due to the hydrophilic properties of isosorbide associated with the proton affinity of the triazine groups. All the phenolic compounds were successfully desorbed from the P6 polymer using a minimal amount of a methanol/acetonitrile mixture. P6 polymer could be used for four successive adsorption processes without loss of efficiency.
KW - Olive mill wastewater
KW - Triazine
KW - Isosorbide
KW - Adsorption
KW - Phenolic compounds
PY - 2024
DO - https://doi.org/10.1007/s42250-024-01081-3
SN - 2522-5758
SP - 1
EP - 11
PB - Springer Science and Business Media LLC
AN - OPUS4-61348
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Barner‐Kowollik, C.
A1 - Falkenhagen, Jana
A1 - Gründling, T.
A1 - Weidner, Steffen
ED - Barner-Kowollik, C.
ED - Gründling, T.
ED - Falkenhagen, Jana
ED - Weidner, Steffen
T1 - Outlook
N2 - The synthesis of macromolecules of an increasing architectural diversity and complexity is the lifeblood of modern macromolecular chemistry, allowing for specialized applications in fields ranging from industrial coatings to medical drug delivery systems. The high complexity of modern polymers with regard to molar mass, chemical functionality, composition, and topology requires a versatile technique for their comprehensive characterization. Today, mass spectrometry, in combination with the soft ionization techniques ESI and MALDI, has been established as an extremely valuable tool for the analysis of polymeric materials.
KW - Mass spectrometry
KW - Polymers
PY - 2012
SN - 978-3-527-32924-3
SN - 978-3-527-64182-6
DO - https://doi.org/10.1002/9783527641826.ch14
SP - 467
EP - 468
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-65739
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Krüger, Rita
A1 - Kelm, Jürgen
A1 - Kretzschmar, Hans-Jürgen
A1 - Schulze, Dietmar
A1 - Trubiroha, Peter
A1 - Weidner, Steffen
T1 - Eine neue Klasse von Ozonschutzmitteln - verbesserter Ozonschutz durch teilweisen Einbau in die Polymermatrix
T2 - IRC '03 ; International Rubber Conference 2003 ; Internationale Kautschuk-Tagung 2003
CY - Nürnberg, Deutschland
DA - 2003-06-30
PY - 2003
SP - 139
EP - 142
PB - DKG, Dt. Kautschuk-Ges.
CY - Frankfurt, Main
AN - OPUS4-2608
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - SnOct2-catalyzed and alcohol-initiated ROPS of L-lactide - Control of the molecular weight and the role of cyclization
N2 - Ring-opening polymerizations (ROP) of l-lactide (LA) are conducted in bulk at 130, 160, or 180 °C and are initiated with two different alcohols at 160 °C. The lactide/initiator ratio (LA/In) is varied from 50/1 (20/1 at 180 °C) to 900/1 and the lactide/catalyst ratio (LA/Cat) between 2000/1 and 8000/1. At all temperatures a nearly perfect control of number average molecular weight (Mn) via the LA/In ratio is feasible up to LA/In = 200/1, but at higher ratios the Mn value lags behind the theoretical values and the discrepancy increases with higher LA/Cat ratios. Variation of the LA/Cat ratio influences the formation of cycles but does not significantly influence Mn, when the LA/In ratio is kept constant. The formation of cycles is favored by lower In/Cat ratios and is the main reason for the unsatisfactory control of Mn at high LA/In ratios. The results also suggest that the cycles are mainly or exclusively formed by end-to-end cyclization and not, as believed previously, by back-biting.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
KW - Ring-opening polymerization
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543066
DO - https://doi.org/10.1002/macp.202100464
SN - 1521-3935
SP - 1
EP - 10
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-54306
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - Syntheses of Polyglycolide via Polycondensation: A Reinvestigation
N2 - The Na salt of chloroacetic acid is condensed in suspension. Furthermore,glycolic acid is condensed in bulk or in concentrated solution by means of SnCl2 or 4-toluene sulfonic acid (TSA) as catalysts. The temperatures are varied from 160 to 200°C and the time from 1 to 5 days. Low molar mass cyclic poly(glycolic acid) (PGA) is detected by means of matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry in most PGAs. A predominance of certain cycles having an even number of repeat units is observed suggesting a thermodynamically favored formation of extended-ring crystals. Extremely high melting temperatures (up to 237.5°C)and high melting enthalpies are found for polycondensations with TSA in 1,2-dichlorobenzene.
KW - MALDI TOF MS
KW - Polycondensation
KW - Polyglycolide
KW - Cyclization
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596856
DO - https://doi.org/10.1002/macp.202300397
IS - 2300397
SP - 1
EP - 7
PB - Wiley VHC-Verlag
AN - OPUS4-59685
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Becker, Roland
A1 - Scholz, Philipp
A1 - Jung, Christian
A1 - Weidner, Steffen
T1 - Thermo-Desorption Gas Chromatography-Mass Spectrometry for investigating the thermal degradation of polyurethanes
N2 - Thermo-Desorption Gas Chromatography-Mass Spectrometry (TD-GC-MS) was used to investigate the thermal degradation of two different polyurethanes (PU). PU samples were heated at different heating rates and the desorbed products were collected in a cold injection system and thereafter submitted to GC-MS. Prospects and limitations of the detection and quantification of semi-volatile degradation products were investigated. A temperature dependent PU depolymerization was
found at temperatures above 200 °C proved by an increasing release of 1,4-butanediol and methylene diphenyl diisocyanate (MDI) representing the main building blocks of both polymers. Their release was monitored quantitatively based on external calibration with authentic compounds. Size Exclusion Chromatography (SEC) of the residues obtained after thermodesorption confirmed the initial competitive degradation mechanism indicating an equilibrium of crosslinking and depolymerization as previously suggested. Matrix-Assisted Laser Desorption Ionization (MALDI) mass spectrometry of SEC fractions of thermally degraded PUs provided additional hints on degradation mechanism.
KW - Thermo-desorption
KW - Mass spectrometry
KW - Polyurethanes
KW - Thermal degradation
PY - 2023
DO - https://doi.org/10.1039/D3AY00173C
SN - 1759-9660
SP - 1
EP - 6
PB - Royal Society for Chemistry
AN - OPUS4-57307
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
A1 - Lahcini, M.
T1 - Poly(epsilon-caprolactone) by combined ring-opening polymerization and polycondensation
N2 - Numerous water-initiated polymerizations of εCL are conducted in bulk with variation of catalyst, reaction time, and temperature. The conversions are determined by 1H NMR and the molar masses by SEC measurements. For polymerizations at 100 °C, Bi triflate and Hf triflate are used as catalysts, whereas at 140 °C, Al triflate, Sn(II) triflate, SnCl2, HfCl4, BiCl3, and LaCl3 are used. In addition to a closed reaction vessel, experiments are also performed with stirring in a vacuum. Under these conditions, the best catalyst (SnCl2) yields 2–3 times higher molar masses and mass spectra indicate a significant higher fraction of cyclic polymers. The results prove that a modification of the procedure may stimulate a polycondesation process without change of catalyst, time, and temperature.
KW - Epsilon-Caprolactone
KW - Cyclization
KW - MALDI-TOF mass spectrometry
KW - Polycondensations
KW - Ring-opening polymerizations
PY - 2012
DO - https://doi.org/10.1002/macp.201200061
SN - 1022-1352
SN - 1521-3935
VL - 213
IS - 14
SP - 1482
EP - 1488
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-26273
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Steinkönig, J.
A1 - Bloesser, F. R.
A1 - Huber, B.
A1 - Welle, A.
A1 - Trouillet, V.
A1 - Weidner, Steffen
A1 - Barner, L.
A1 - Roesky, P. W.
A1 - Yuan, J.
A1 - Goldmann, A. S.
A1 - Barner-Kowollik, C.
T1 - Controlled radical polymerization and in-depth mass-spectrometric characterization of poly(ionic liquid)s and their photopatterning on surfaces
N2 - The preparation and characterization of poly(ionic liquid)s (PILs) bearing a polystyrene backbone via reversible addition fragmentation chain transfer (RAFT) polymerization and their photolithographic patterning on silicon wafers is reported. The controlled radical polymerization of the styrenic ionic liquid (IL) monomers ([BVBIM]X, X = Cl− or Tf2N−) by RAFT polymerization is investigated in detail. We provide a general synthetic tool to access this class of PILs with controlled molecular weight and relatively narrow molecular weight distribution (2000 g mol−1 ≤ Mn ≤ 10 000 g mol−1 with dispersities between 1.4 and 1.3 for p([BVBIM]Cl); 2100 g mol−1 ≤ MP ≤ 14 000 g mol−1 for p([BVBIM]Tf2N)). More importantly, we provide an in-depth characterization of the PILs and demonstrate a detailed mass spectrometric analysis via matrix-assisted laser desorption ionization (MALDI) as well as – for the first time for PILs – electrospray ionization mass spectrometry (ESI-MS). Importantly, p([BVBIM]Cl) and p([DMVBIM]Tf2N) were photochemically patterned on silicon wafers. Therefore, a RAFT agent carrying a photoactive group based on ortho-quinodimethane chemistry – more precisely photoenol chemistry – was photochemically linked for subsequent controlled radical polymerization of [BVBIM]Cl and [DMVBIM]Tf2N. The successful spatially-resolved photografting is evidenced by surface-sensitive characterization methods such as X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The presented method allows for the functionalization of diverse surfaces with poly(ionic liquid)s.
KW - reversible addition fragmentation chain transfer (RAFT) polymerization
KW - polyionic liquids
KW - mass spectrometry
KW - surface modification
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-355202
DO - https://doi.org/10.1039/C5PY01320H
VL - 7
SP - 451
EP - 461
PB - Royal Society of Chemistry
CY - Cambridge
AN - OPUS4-35520
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zydziak, N.
A1 - Konrad, W.
A1 - Feist, F.
A1 - Afonin, S.
A1 - Weidner, Steffen
A1 - Barner-Kowollik, C.
T1 - Coding and decoding libraries of sequence-defined functional copolymers synthesized via photoligation
N2 - Designing artificial macromolecules with absolute sequence order represents a considerable challenge. Here we report an advanced light-induced avenue to monodisperse sequencedefined functional linear macromolecules up to decamers via a unique photochemical approach. The versatility of the synthetic strategy—combining sequential and modular concepts—enables the synthesis of perfect macromolecules varying in chemical constitution and topology. Specific functions are placed at arbitrary positions along the chain via the successive addition of monomer units and blocks, leading to a library of functional homopolymers, alternating copolymers and block copolymers. The in-depth characterization of each sequence-defined chain confirms the precision nature of the macromolecules. Decoding of the functional information contained in the molecular structure is achieved via tandem mass spectrometry without recourse to their synthetic history, showing that the sequence information can be read.We submit that the presented photochemical strategy is a viable and advanced concept for coding individual monomer units along a macromolecular chain.
KW - Photoligation
KW - Copolymer sequence
KW - MALDI-TOF MS/MS
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-391542
DO - https://doi.org/10.1038/ncomms13672
SN - 2041-1723
VL - 7
SP - Artikel Nr. 13672
AN - OPUS4-39154
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Diehn, Sabrina
A1 - Zimmermann, B.
A1 - Bagcioglu, M.
A1 - Seifert, Stephan
A1 - Kohler, A.
A1 - Ohlson, M.
A1 - Fjellheim, S.
A1 - Weidner, Steffen
A1 - Kneipp, Janina
T1 - Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) shows adaption of grass pollen composition
N2 - MALDI time-of-flight mass spectrometry (MALDI-TOF MS) has become a widely used tool for the classification of biological samples. The complex chemical composition of pollen grains leads to highly specific, fingerprint-like mass spectra, with respect to the pollen species. Beyond the species-specific composition, the variances in pollen chemistry can be hierarchically structured, including the level of different populations, of environmental conditions or different genotypes. We demonstrate here the sensitivity of MALDI-TOF MS regarding the adaption of the chemical composition of three Poaceae (grass) pollen for different populations of parent plants by analyzing the mass spectra with partial least squares discriminant analysis (PLS-DA) and principal component analysis (PCA). Thereby, variances in species, population and specific growth conditions of the plants were observed simultaneously. In particular, the chemical pattern revealed by the MALDI spectra enabled discrimination of the different populations of one species. Specifically, the role of environmental changes and their effect on the pollen chemistry of three different grass species is discussed. Analysis of the Group formation within the respective populations showed a varying influence of plant genotype on the classification, depending on the species, and permits conclusions regarding the respective rigidity or plasticity towards environmental changes.
KW - Pollen
KW - MALDI-TOF MS
KW - Classification
KW - Partial least square discriminant analysis (PLS-DA)
KW - Principal component analysis (PCA)
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-465294
DO - https://doi.org/10.1038/s41598-018-34800-1
SN - 2045-2322
VL - 8
IS - 1
SP - 16591, 1
EP - 11
PB - Nature
AN - OPUS4-46529
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Meyer, A.
A1 - Weidner, Steffen
A1 - Kricheldorf, H.
T1 - Stereocomplexation of cyclic polylactides with each other and with linear poly(L-lactide)s
N2 - Two kinds of cyclic poly(D- and L-lactide)s were synthesized, namely CI labeled samples mainly consisting of even-numbered cycles with low dispersity and CII, CIII or CIV-labeled ones consisting of equal amounts of even and odd-numbered cycles with high dispersity and igher molecular weights (Mw up to 300 000). Furthermore, linear poly L-lactide)s were prepared by initiation with ethanol and in both series the molecular weight was varied. The formation of stereocomplexes from cyclic poly(D-lactide)s and all kinds of poly L-lactide)s was performed in dichloromethane/toluene mixtures. The stereocomplexes crystallized from the reaction mixture were characterized in the virgin state and after annealing at 205 °C.
Stereocomplexes free of stereohomopolymers with crystallinities up to 80% were obtained from all experiments in yields ranging from 60 to 80%. Despite the high annealing temperature (maintained for 1 h), little transesterification was observed and the crystallinity slightly increased.
KW - Polylactide
KW - MALDI-TOF MS
KW - Stereocomplex
KW - Cyclic
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-496693
DO - https://doi.org/10.1039/c9py01236b
VL - 10
SP - 6191
EP - 6199
PB - Royal Society for Chemistry
AN - OPUS4-49669
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Synthesis of cyclic polymers and flaws of the Jacobson–Stockmayer theory
N2 - Cyclic poly(L-lactide)s were prepared by ring-opening polymerization combined with simultaneous polycondensation (ROPPOC) in bulk at 160 ° with dibutyltin bis(4-cyanophenoxide) as catalyst. It is demonstrated by MALDI TOF mass spectrometry and 1H NMR end group analyses that cycles are formed by endto-end cyclization in addition to “back-biting” transesterification. Formation of high molar mass cyclic poly L-lactide)s by means of several more reactive ROPPOC catalysts presented previously and in new experiments is discussed. These experimental results, together with theoretical arguments, prove that part of the Jacobson–Stockmayer theory is wrong. The critical monomer concentration, above which end-toend cyclization is seemingly impossible, does not exist and reversible like irreversible polycondensations can theoretically proceed up to 100% conversion, so that finally all reaction products will necessarily adopt a cyclic architecture.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506419
DO - https://doi.org/10.1039/d0py00226g
VL - 11
IS - 14
SP - 2595
EP - 2604
PB - Royal Society for Chemistry
AN - OPUS4-50641
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lauer, Franziska
A1 - Seifert, Stephan
A1 - Kneipp, Janina
A1 - Weidner, Steffen
T1 - Simplifying the Preparation of Pollen Grains for MALDI-TOF MS Classification
N2 - Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) is a well-implemented analytical technique for the investigation of complex biological samples. In MS, the sample preparation strategy is decisive for the success of the measurements. Here, sample preparation processes and target materials for the investigation of different pollen grains are compared. A reduced and optimized sample preparation process prior to MALDI-TOF measurement is presented using conductive carbon tape as target. The application of conductive tape yields in enhanced absolute signal intensities and mass spectral pattern information, which leads to a clear separation in subsequent pattern analysis. The results will be used to improve the taxonomic differentiation and identification, and might be useful for the development of a simple routine method to identify pollen based on mass spectrometry.
KW - PCA
KW - MALDI-TOF MS
KW - Conductive carbon tape
KW - Pollen
KW - Sample pretreatment
PY - 2017
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-392885
UR - http://www.mdpi.com/1422-0067/18/3/543/
DO - https://doi.org/10.3390/ijms18030543
SN - 1422-0067
VL - 18
IS - 3
SP - 543
EP - 554
PB - MDPI AG
CY - Basel, Switzerland
AN - OPUS4-39288
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Synthesis of cyclic poly(l-lactide) catalyzed by Bismuth salicylates-A combination of two drugs
N2 - l‐lactide was polymerized in bulk at 160 or 180°C with mixtures of bismuth subsalicylate (BiSub) and salicylic (SA) as catalysts. The SA/Bi ratio and the monomer/Bi ratio were varied. The highest molecular weights (weight average, Mw) were achieved at a SA/Bi ratio of 1/1 (Mw up to 92 000 g mol−1). l‐Lactide was also polymerized with combinations of BiSub and silylated SA, and Mw values up to 120 000 g mol−1 were achieved at 180°C. MALDI‐TOF mass spectrometry and Mark‐Houwink‐Sakurada measurements proved that under optimized reaction conditions the resulting polylactides consist of cycles.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
KW - Catalyst
KW - Salicylate
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488622
DO - https://doi.org/10.1002/pola.29473
SN - 0887-624X
SN - 1099-0518
SP - 29473
PB - Wiley
AN - OPUS4-48862
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H. R.
T1 - Ring–Ring Equilibration in Solid, Even-Numbered Cyclic Poly(l-lactide)s and their Stereocomplexes
N2 - Even-numbered cyclic poly(d-lactide) and poly(l-lactide) are prepared by ringexpansion polymerization. The cyclic pol(l-lactide) is annealed either at 120 or at 160 °C for several days. The progress of transesterification in the solid state is monitored by the formation of odd-numbered cycles via matrix-assisted laser desorption/ionization-time of flight mass spectrometry. The changes of the crystallinity are monitored by differential scanning calorimetry, wideand small-angle x-ray scattering (WAXS and SAXS) measurements. Despite total even-odd equilibration at 160 °C, the crystallinity of poly(l-lactide) is not reduced. Furthermore, the crystallinity of the stereocomplexes of both cyclic polylactides do not decrease or vanish, as expected, when a blocky or random stereosequence is formed by transesterification. This conclusion is confirmed by 13C NMR spectroscopy. These measurements demonstrate that transesterification is a ring–ring equilibration involving the loops on the surfaces of the lamellar crystallites thereby improving crystallinity and 3D packing of crystallites without significant broadening of the molecular weight distribution.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506458
DO - https://doi.org/10.1002/macp.202000012
VL - 221
IS - 9
SP - 2000012
PB - Wiley-VCH Verlag
AN - OPUS4-50645
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Doriti, A.
A1 - Brosnan, S.
A1 - Weidner, Steffen
A1 - Schlaad, H.
T1 - Synthesis of polysarcosine from air and moisture stable N-phenoxycarbonyl-N-methylglycine assisted by tertiary amine base
N2 - Polysarcosine (M-n = 3650-20 000 g mol(-1), D similar to 1.1) was synthesized from the air and moisture stable N-phenoxycarbonyl-N-methylglycine. Polymerization was achieved by in situ transformation of the urethane precursor into the corresponding N-methylglycine-N-carboxyanhydride, when in the presence of a non-nucleophilic tertiary amine base and a primary amine initiator.
KW - Polysarcosine
KW - MALDI-TOF MS
KW - Synthesis
PY - 2016
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-359309
DO - https://doi.org/10.1039/c6py00221h
SN - 1759-9954
SN - 1759-9962
VL - 7
IS - 18
SP - 3067
EP - 3070
AN - OPUS4-35930
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Synthesis of polylactides by means of tin catalysts
N2 - This article reviews the usefulness of tin(II) and tin(IV) salts and compounds as catalysts for the polymerization of lactides. The text is subdivided into nine parts mainly reflecting different polymerization strategies, such as ring-opening polymerization (ROP), ring-expansion polymerization (REP), ROP combined with simultaneous polycondensation (ROPPOC), various catalysts with unknown polymerization mechanisms, and polycondensation of lactic acid. Since the toxicity of tin salts and compounds is a matter of concern and frequently mentioned in numerous publications, the first section deals with facts instead of myths about the toxicity of tin salts and compounds.
KW - Polylactide
KW - MALDI-TOF MS
KW - Tin catalysts
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545050
DO - https://doi.org/10.1039/d2py00092j
SP - 1
EP - 30
PB - Royal Society for Chemistry
AN - OPUS4-54505
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
T1 - Ring-ring equilibration (RRE) of cyclic poly(L-lactide)s by means of cyclic tin catalysts
N2 - With 2,2-dibutyl-2-stanna-1,3-dithiolane (DSTL) and 2-stanna-1,3-dioxa-4,5,6,7-dibenzoxepane (SnBiPh) as catalysts ring-expansion polymerizations (REP) were performed either in 2 M solution using three different solvents and two different temperatures or in bulk at 140 and 120 ◦C. A kinetically controlled rapid REP up to weight average molecular masses (Mẃs) above 300 000 was followed by a slower degradation of the molecular masses at 140 ◦C, but not at 120 ◦C Furthermore, a low molecular mass cyclic poly(L-lactide) (cPLA) with a Mn around 16 000 was prepared by polymerization in dilute solution and used as starting material for ring-ring equilibration at 140 ◦C in 2 M solutions. Again, a decrease of the molecular mass was detectable, suggesting that the equilibrium Mn is below 5 000. The degradation of the molecular masses via RRE was surprisingly more effective in solid cyclic PLA than in solution, and a specific transesterification mechanism involving loops on the surface of crystallites is proposed. This degradation favored the formation of extended-ring crystallites, which were detectable by a “saw-tooth pattern” in their MALDI mass spectra.
KW - Organic Chemistry
KW - Polymers and Plastics
KW - MALDI-TOF MS
KW - Materials Chemistry
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-593819
DO - https://doi.org/10.1016/j.eurpolymj.2024.112765
SN - 0014-3057
VL - 206
SP - 1
EP - 8
PB - Elsevier B.V.
AN - OPUS4-59381
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Falkenhagen, Jana
A1 - Kricheldorf, H. R.
T1 - Polycondensations and Cyclization of Poly(L-lactide) Ethyl Esters in the Solid State
N2 - The usefulness of seven different Tin catalysts, Bismuth subsalicylate and Titan tetra(ethoxide) for the polycondensation of ethyl L-lactate (ELA) was examined at 150 °C/6 d. Dibutyltin bis(phenoxides) proved to be particularly effective. Despite the low reactivity of ELA, weight average molecular masses (Mw) up to 12 500 were found along with partial crystallization. Furthermore, polylactides (PLAs) of similar molecular masses were prepared via ELA-initiated ROPs of L-lactide by means of the four most effective polycondensation catalysts. The crystalline linear PLAs were annealed at 140 or 160 °C in the presence of these catalysts. The consequences of the transesterification reactions in the solid PLAs were studied by means of matrix-assisted laser desorption/ionization (MALDI TOF) mass spectrometry, gel permeation chromatography (GPC) and small-angle X-ray scattering (SAXS). The results indicate that polycondensation and formation of cycles proceed in the solid state via formation of loops on the surface of the crystallites. In summary, five different transesterification reactions are required to explain all results.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-592934
DO - https://doi.org/10.1039/d3py01232h
SN - 1759-9962
VL - 15
IS - 2
SP - 71
EP - 82
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-59293
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Martins, Ines
A1 - Al-Sabbagh, Dominik
A1 - Bentrup, U.
A1 - Marquardt, Julien
A1 - Schmid, Thomas
A1 - Scoppola, E.
A1 - Kraus, Werner
A1 - Stawski, Tomasz
A1 - de Oliveira Guilherme Buzanich, Ana
A1 - Yusenko, Kirill
A1 - Weidner, Steffen
A1 - Emmerling, Franziska
T1 - Formation Mechanism of a Nano-Ring of Bismuth Cations and Mono-Lacunary Keggin-Type Phosphomolybdate
N2 - A new hetero-bimetallic polyoxometalate (POM) nano-ring was synthesized in a one-pot procedure. The structure consists of tetrameric units containing four bismuth-substituted monolacunary Keggin anions including distorted [BiO8] cubes. The nano-ring is formed via self-assembly from metal precursors in aqueous acidic medium. The compound (NH4)16[(BiPMo11O39)4] ⋅ 22 H2O; (P4Bi4Mo44) was characterized by single-crystal X-ray diffraction, extended X-ray absorption fine structure spectroscopy (EXAFS), Raman spectroscopy, matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF), and thermogravimetry/differential scanning calorimetry mass spectrometry (TG-DSC-MS). The formation of the nano-ring in solution was studied by time-resolved in situ small- and wide-angle X-ray scattering (SAXS/WAXS) and in situ EXAFS measurements at the Mo−K and the Bi−L3 edge indicating a two-step process consisting of condensation of Mo-anions and formation of Bi−Mo-units followed by a rapid self-assembly to yield the final tetrameric ring structure.
KW - Bismuth
KW - In situ EXAFS
KW - In situ SAXS/WAXS
KW - Lacunary Keggin ion
KW - Polyoxometalates
KW - Self-assembly
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546823
DO - https://doi.org/10.1002/chem.202200079
SN - 0947-6539
VL - 28
IS - 27
SP - 1
EP - 7
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-54682
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Scheliga, F.
A1 - Weidner, Steffen
T1 - Syntheses of Cyclic Poly(l-lactide)s by Means of Zinc-Based Ring-Opening Polymerization with Simultaneous Polycondensation (ROPPOC) Catalysts
N2 - Ring-opening polymerizations of l-lactide are studied in bulk at 140 or 160 °C with zinc n-hexanoate, zinc 4-chlorothiophenolate, and zinc pentafluoro thiophenolate (ZnSPF) as catalysts. The reactivity increases in the given order.
With all three catalysts a high fraction of cycles is obtained only at polymerization (annealing) times around 7 d. With ZnSPF weight average molecular weights (Mw) up to 178 000, a Tm around 199 °C and a 𝚫Hm around 99 J g−1 were achieved. The samples annealed for 4 or 7 d also display a saw tooth pattern of the mass peak distribution in the matrix-assisted laser desorption/ionization time of flight spectra indicating transesterification reactions across the surface of extended ring crystals. This process optimizes the thermodynamical properties of the crystalline cyclic polylactides and is responsible for the high Tm and 𝚫Hm values.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring opening polymerization
KW - Polymerization
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-578264
DO - https://doi.org/10.1002/macp.202300070
SN - 1022-1352
SP - 202300070
PB - Wiley VHC-Verlag
AN - OPUS4-57826
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Ring-opening polymerizations of L-Lactide catalyzed by zinc caprylate: Syntheses of cyclic and linear poly(L-lactide)s
N2 - Alcohol-initiated ring-opening polymerizations (ROPs) of L-Lactide (LA) were conducted in bulk at 130 °C catalyzed by Zn acetate (ZnAc2), lactate (ZnLac2), or caprylate (ZnCap2). 11-undecenol (UND), 1-hydroxymethylnaphtalene (HMN), and 4-nitrobenzylalcohol (4NB) were used as alcohols. Whereas variation of the alcohols had little effect, the usefulness of the catalysts increased in the order: acetate < lactate < caprylate. Hence, further alcohol-initiated polymerizations were performed with ZnCap2 alone and with variation of the lactide/catalyst (LA/Cat) ratio. With increasing LA/Cat ratio higher fractions of cyclic poly(L-lactide) (PLA) were found, so that the measured degree of polymerization (DP) is considerably lower than the theoretical value (i.e., 2 x LA/alcohol). With neat ZnCap2 cyclic PLAs were the largely prevailing reaction products. For these cyclic PLAs weight average molar masses (Mw) up to 134,000 were obtained and an optical purity around 99% was indicated by 13C NMR spectroscopy and DSC measurements even after 48 h at 150 or 160 °C.
KW - Cyclization
KW - Lactide
KW - Ring opening polymerization
KW - Transesterification
KW - Zinc catalyst
KW - MALDI
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-557565
DO - https://doi.org/10.1002/pol.20220328
SN - 2642-4150
SP - 1
EP - 10
PB - Wiley
AN - OPUS4-55756
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
T1 - Cyclic and linear poly(L-lactide)s by ring-expansion polymerization with Bu2SnO, Oct2SnO, and Bu2SnS
N2 - To elucidate the usefulness of commercial Bu2SnO as catalyst for syntheses of linear and/or cyclic polylactides L-Lactide was polymerized in bulk with variation of the LA/Cat ratio, temperature and time. Based on a ring-expansion polymerization (REP) mechanism cyclic polylactides (PLAs) with weight average molecular weights in the range of 200,000–300,000 are obtained at the highest temperature (180 °C). Polymerizations at 150 °C yielded crystalline, mainly cyclic polylactides which, after annealing, showed high melting temperatures (up to 197.5 °C) and high crystallinities (>80%). Polymerization at 120 °C confirmed the trend towards more linear chains with lower temperatures but yielded extended-ring crystals showing a “saw-tooth pattern” in the mass spectra. Oct2SnO gave similar results as Bu2SnO. Bu2SnS proved a sluggish polymerization catalyst, but a good transesterification catalyst in solid PLA.
KW - MALDI TOF MS
KW - Biobased polymers
KW - Polylactide
KW - Ring-expansion polymerization
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-584121
DO - https://doi.org/10.1002/pol.20230515
SN - 2642-4169
SP - 1
EP - 10
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-58412
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - About the Influence of (Non-)Solvents on the Ring Expansion Polymerization of l-Lactide and the Formation of Extended Ring Crystals
N2 - Ring-expansion polymerizations (REPs) catalyzed by two cyclic tin catalysts (2-stanna-1.3-dioxa-4,5,6,7-dibenzazepine [SnBiph] and
2,2-dibutyl-2-stanna-1,3-dithiolane [DSTL]) are performed at 140 °C in bulk.
Small amounts (4 vol%) of chlorobenzene or other solvents are added to
facilitate transesterification reactions (ring–ring equilibration) in the solid poly(l-lactide)s. In the mass range up to m/z 13 000 crystalline PLAs displaying a so-called saw-tooth pattern in the MALDI-TOF mass spectra are obtained indicating the formation of extended-ring crystals. The characteristics of extended-ring crystallites and folded-ring crystallites are discussed. Furthermore, extremely high melting temperatures (Tm’s up to 201.2 °C) and melting enthalpies (𝚫Hm’s up to 106 J g−1)) are found confirming that 𝚫Hm max, the 𝚫Hm of a perfect crystal, is around or above 115 J g−1 in contrast to literature data.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring-expansion polymerization
KW - Biobased
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-573063
DO - https://doi.org/10.1002/macp.202200385
VL - 224
IS - 5
SP - 1
EP - 8
PB - Wiley VHC-Verlag
AN - OPUS4-57306
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans. R.
A1 - Weidner, Steffen
T1 - About the Toxicity of Polymerization Catalysts and Polymer Additives Based on Tin(II) Salts and Tin(IV) Compounds
N2 - This article reviews and discusses information on the toxicity of numerous tin-based catalysts used in academic research and industrial production for the synthesis of various polymers, such as polyesters, polyurethanes, and polysiloxanes. Tin(IV) compounds used as additives and as PVC stabilizers are also considered. Emphasis is put on the differentiation between tin(II) salts on the one hand and tin(IV) compounds on the other hand. In the first chapter, historical facts about human contact with stannous ions are discussed, along with toxicity studies of canned foods and beverages. In the second part, toxicity tests based on cell cultures and medical applications of tin(II)-containing films or implants are described. The third part focuses on alkyl and aryl tin(IV) compounds.
KW - Tin
KW - Toxicity
KW - Environment
KW - Polymer catalysts
KW - Polymer additives
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-642877
DO - https://doi.org/10.1021/acs.chas.5c00105
SN - 1871-5532
SP - 1
EP - 13
PB - American Chemical Society (ACS)
AN - OPUS4-64287
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Meyer, Andreas
A1 - Weidner, Steffen
A1 - Kricheldorf, Hans R.
T1 - Star-shaped poly(l-lactide)s based on pentaerythritol: About crystallization and polycondensation plus disproportionation and ring formation in the solid state
N2 - Star-shaped poly( L-lactide)s (s-PLAs), were prepared by ring-opening polymerization of with pentaerythritol and catalyzed by tin(II) 2-ethylhyexanoate (SnOct out in bulk at either 120 ◦ C or 160 ◦ L-lactide (LA) initiated 2 ). Two small series of ROPs were carried C with variation of the LA/initiator ratio. Matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) mass spectra revealed traces of cycles in 120 ◦ C samples only at low initiator/catalyst ratios. In contrast, higher fractions of cycles were detected in samples prepared at 160 C, suggesting a "back-biting" origin. The influence of arm length and thermal history on crystallinity was investigated by differential scanning calorimetry (DSC) and wide-angle x-ray scattering (WAXS). It was shown that annealing increased the melting temperature (T ◦ ◦ m ) and crystallinity. However, annealing at 140 ◦ C for 14 d also caused significant solid-state transesterification. In addition, crystallites composed of s-PLAs with extended arms and, simultaneously, crystallites composed exclusively of extended rings were formed, identified by their typical "sawtooth" pattern in the MALDI mass spectra. Small angle x-ray scattering (SAXS) indicated that the crystal thickness was lower than that of linear PLAs annealed under identical conditions, but increased upon annealing at 140 C.
KW - MALDI-TOF MS
KW - Polylactide
KW - Crystallisation
KW - AStar-shaped polymers
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636832
DO - https://doi.org/10.1016/j.polymer.2025.128709
SN - 0032-3861
VL - 334
SP - 1
EP - 11
PB - Elsevier Ltd.
AN - OPUS4-63683
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Rösler, Alexander
A1 - Weidner, Steffen
A1 - Klamroth, Tillmann
A1 - Müller, Axel H. E.
A1 - Schlaad, Helmut
T1 - Kinetics of anionic polymerization of β‐myrcene in hydrocarbon solvents
N2 - The kinetics of anionic polymerization of β‐myrcene initiated by sec‐butyllithium were examined in saturated and unsaturated hydrocarbon solvents, i.e. cyclohexane, cyclohexene, 4‐vinylcyclohexene and dl‐limonene. Polymerizations usually proceeded in a living manner, i.e. in the absence of termination and chain transfer reactions, in all solvents, to produce well‐defined polymyrcenes with high content (85%) of cis‐1,4 units. However, polymyrcenyllithium chains exhibited limited long‐term stability in 4‐vinylcyclohexene solution, most probably due to chain transfer to solvent. Reaction orders with respect to the concentration of active chains were found to be one‐quarter in cyclohexane increasing to one‐half in unsaturated solvents, indicating that the polymyrcenyllithium chains are present as tetrameric or dimeric associates, respectively. Apparent activation energies were found to be 81 kJ mol−1 in cyclohexane and 77 kJ mol−1 in dl‐limonene solution, which are close to the values obtained by quantum chemical calculations.
KW - MALDI-TOF MS
KW - Anionic polymerization
KW - β‐myrcene
KW - Kinetics
KW - Reaction order
KW - Activation energy
KW - Microstructure
KW - Quantum chemical calculations
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630900
DO - https://doi.org/10.1002/pi.6772
SN - 1097-0126
SP - 1
EP - 8
PB - Wiley
CY - New York, NY
AN - OPUS4-63090
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
T1 - Polymerization of L‐Lactide Catalyzed by Metal Acetylacetonate Complexes
N2 - ABSTRACTRing‐opening polymerizations (ROPs) of l‐lactide (LA) were performed at 120°C, 140°C, 150°C, and 180°C in bulk catalyzed by acetylacetonate (acac) complexes of manganese(II), nickel(II), copper(II), zirconium(IV), dibutyltin(IV), and vanadyl(V). These experiments revealed that only the acac complexes of Zr and Bu2Sn were reactive enough to enable quantitative polymerization within a few hours. Further ROPs with Bu2Sn(acac)2 and Zr(acac)4 showed that Bu2Sn(acac)2 had a slightly lower reactivity than the Zr complex. The ROPs catalyzed with Zr(acac)4 yielded number average molecular weights (Mn) up to 70,000 g mol−1. The matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra indicated an exclusive formation of cycles in the mass range of up to m/z 13,000 for Zr(acac)4 and up to m/z 18,000 for Bu2Sn(acac)2. Unusually high melting temperatures (187°C–192°C) were also achieved along with high crystallinities. Furthermore, four lactide/glycolide copolymerizations catalyzed by Zr(acac)4 were performed, and the topology and the extent of transesterification were characterized by MALDI‐TOF mass spectrometry and 13C NMR spectroscopy.
KW - MALDI-TOF MS
KW - Polycondensation
KW - Acetylacetonate
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-639754
DO - https://doi.org/10.1002/pol.20250788
SN - 2642-4150
SP - 1
EP - 9
PB - Wiley Periodicals LLC.
AN - OPUS4-63975
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
T1 - Zwitterionic polymerization of glycolide catalyzed by pyridine
N2 - The usefulness of various N- and P-based catalysts for syntheses of cyclic polyglycolide via zwitterionic polymerization of glycolide was examined. Most catalysts produced discolored, largely insoluble polyglycolides consisting of cycles and unidentified byproducts. Soluble, cyclic polyglycolides were obtained using neat pyridine as catalyst at 120 °C, 100 °C, 80 °C, and even at 60 °C. The number-average molecular weights were extremely low and depended slightly on the glycolide-to-pyridine ratio. Three different mass distributions of the cycles were detected by mass spectrometry, depending on the reaction conditions. The cyclic polyglycolides were also characterized by differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) measurements. The SAXS data in combination with the mass spectra indicate that the majority of the cycles form extended-ring crystallites
KW - MALDI-TOF MS
KW - Polylactide
KW - Polymerization
KW - Zitterions
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-639748
DO - https://doi.org/10.1039/d5py00762c
SN - 1759-9954
SP - 1
EP - 9
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-63974
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Rösler, Alexander
A1 - Weidner, Steffen
A1 - Klamroth, Tillmann
A1 - Müller, Axel HE
A1 - Schlaad, Helmut
T1 - Kinetics of anionic polymerization of β‐myrcene in hydrocarbon solvents
N2 - AbstractThe kinetics of anionic polymerization of β‐myrcene initiated by sec‐butyllithium were examined in saturated and unsaturated hydrocarbon solvents, i.e. cyclohexane, cyclohexene, 4‐vinylcyclohexene and dl‐limonene. Polymerizations usually proceeded in a living manner, i.e. in the absence of termination and chain transfer reactions, in all solvents, to produce well‐defined polymyrcenes with high content (85%) of cis‐1,4 units. However, polymyrcenyllithium chains exhibited limited long‐term stability in 4‐vinylcyclohexene solution, most probably due to chain transfer to solvent. Reaction orders with respect to the concentration of active chains were found to be one‐quarter in cyclohexane increasing to one‐half in unsaturated solvents, indicating that the polymyrcenyllithium chains are present as tetrameric or dimeric associates, respectively. Apparent activation energies were found to be 81 kJ mol−1 in cyclohexane and 77 kJ mol−1 in dl‐limonene solution, which are close to the values obtained by quantum chemical calculations. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
KW - Myrcene
KW - Anionic polymerization
KW - Reaction order
KW - Activation energy
KW - Microstructure
KW - Quantum chemical calculation
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636840
DO - https://doi.org/10.1002/pi.6772
SN - 0959-8103
SP - 1
EP - 8
PB - Wiley
AN - OPUS4-63684
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bui, Minh
A1 - Heinekamp, Christian
A1 - Fuhry, Emil
A1 - Weidner, Steffen
A1 - Radnik, Jörg
A1 - Ahrens, Mike
A1 - Scheurell, Kerstin
A1 - Balasubramanian, Kannan
A1 - Emmerling, Franziska
A1 - Braun, Thomas
T1 - Lewis-acid induced mechanochemical degradation of polyvinylidene fluoride: transformation into valuable products
N2 - Polyvinylidene fluoride (–[CH2CF2]n–, PVDF) waste poses significant environmental challenges due to its recalcitrant nature and widespread use. This study addresses the end-of-life management of PVDF by introducing a novel, sustainable mechanochemical approach for its valorisation. We investigated the degradation of PVDF into value-added materials using ball milling with anhydrous AlCl3 to achieve a quantitative mineralisation producing AlF3 and halide-functionalised graphite, along with gaseous products (HCl and CH4). Mechanistic key steps involve Lewis-acid catalysed C–F bond activation, dehydrofluorination and aromatisation. This approach provides an effective solution for PVDF waste management while offering a promising route for the production of high-value materials from polymer waste streams. Our findings contribute to sustainable practices in polymer recycling and resource recovery, respond to pressing environmental concerns associated with fluoropolymer disposal, and demonstrate the potential to convert polymer wastes into useful products.
KW - Mechanochemistry
KW - Polyvinylidenfluoride
KW - Degradation
KW - Ball mill
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-649015
DO - https://doi.org/10.1039/d5sc05783c
SN - 2041-6520
VL - 16
IS - 40
SP - 18903
EP - 18910
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-64901
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - About Polycondensation, Disproportionation, and Cyclization of Acetylated Poly(L-Lactide) Esters
N2 - L-lactide (LA) is polymerized with ethyl L-lactate or trifluoroethanol as initiators (LA/In = 30/1), and the resulting poly(L-lactide) esters are acetylated with acetic anhydride. The acetylated PLA esters are mixed with SnOct2, dibutyltin bis(4-chlorophenoxide), or dibutyltin bis(pentafluorophenoxide) in solution and crystallized at 120 °C. The doped crystals are annealed at 140 °C or at 160 °C for 7, 14, and 28 days, and the chemical modifications that occurred in the solid state are monitored by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) measurements. All catalysts promoted polycondensation, while no significant formation of cycles is observed. However, in the presence of SnOct2, disproportionation of chains occurred upon annealing at 120 or 140 °C, and crystallites consisting of extended chains with Mn values ≈3500 – 3600 and low dispersities (Ð < 1.5) are formed.
KW - MALDI-TOF MS
KW - Polycondensation
KW - Polylactides
KW - Transesterifcation
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630349
DO - https://doi.org/10.1002/macp.202400175
SN - 1521-3935
VL - 225
IS - 19
PB - Wiley VHC-Verlag
AN - OPUS4-63034
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
A1 - Meyer, Andreas
T1 - Poly(butylene terephthalate): About condensation, cyclization, degradation and elimination reactions in the solid state, and the role of smooth crystal surfaces
N2 - Three commercial poly(butylene terephthalate) (PBT) samples - Pocan B1300 (B13), Pocan B1600 (B16), and Addigy P 1210 (AP121) - served as the starting materials for the annealing experiments, which were conducted with and without the addition of esterification and transesterification catalysts. The catalysts used were Sn(II) 2-ethylhexanoate (SnOct₂), Zr(IV) acetylacetonate, and 4-toluene sulfonic acid (TSA). Temperatures varied between 150 and 210 °C. The PBT samples were characterized using differential scanning calorimetry (DSC), gel permeation chromatography (GPC), small-angle X-ray scattering (SAXS), and matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry. The MALDI mass spectra of all three samples differed greatly but displayed mass peaks of cycles. Similar results were produced by annealing with SnOct₂ or Zr(acac)₄, which favored the formation of even-numbered cycles within the mass range below m/z 5000, along with slow degradation. TSA favored a more intensive degradation without the formation of cycles or even with the destruction of cycles. PBT chains with two carboxylic (COOH) end groups were the most stable species under all circumstances. The origin of the extremely high melting point of AP121 (241–242 °C) can be explained by the smoothing of crystallite surfaces via transesterification. The results suggest that combining MALDI mass spectrometry and SAXS measurements provides a new way to better understand the solid-state chemistry of PBT and related polyesters.
KW - MALDI-TOF MS
KW - Polybutylene Terephthalate
KW - Crystallization
KW - solid state
KW - cyclization
PY - 2026
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-652844
DO - https://doi.org/10.1016/j.polymdegradstab.2025.111862
SN - 0141-3910
VL - 245
SP - 1
EP - 11
PB - Elsevier Ltd.
AN - OPUS4-65284
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dalgic, Mete‐Sungur
A1 - Kumar, Sourabh
A1 - Weidner, Steffen
T1 - Quantitative Analysis of Polymers by MALDI‐TOF Mass Spectrometry: Correlation Between Signal Intensity and Arm Number
N2 - The signal intensities of linear and star‐shaped poly(L‐lactides) (PLA) and poly (ethylene oxides) (PEO) were compared to determine the influence of the number of arms on the ionization in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. In this study, a variety of blends were prepared and investigated, including binary and ternary combinations of linear and star‐shaped polymers with similar molecular masses. The focus was on examining their intensity ratios. In equimolar binary PLA blends, polymer stars were observed to exhibit higher intensities than their linear counterparts. This result was supported by experiments with equimolar ternary PLA blends, which clearly demonstrated an intensity dependence on the number of polymer arms. It was observed that four‐arm PLA exhibited higher intensities than three‐arm PLA. A similar trend was observed in investigations involving acetylated polymer end groups, suggesting that differences in ionization are primarily influenced by polymer architecture rather than end groups. In order to validate this assumption, the binding energies for [polymer‐K] + adduct ions utilizing the most stable geometry obtained from GOAT (Global Optimizer Algorithm) were calculated, revealing that star‐shaped lower mass oligomers have slightly higher binding energies.
KW - MALDI-TOF MS
KW - Starlike polymers
KW - Quantification
KW - Topology
PY - 2026
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-653401
DO - https://doi.org/10.1002/jms.70023
SN - 1076-5174
VL - 61
IS - 1
SP - 1
EP - 12
PB - John Wiley & Sons Ltd.
AN - OPUS4-65340
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, Andreas
A1 - Falkenhagen, Jana
A1 - Kricheldorf, Hans R.
T1 - Cyclic polyglycolide by means of metal acetylacetonates
N2 - Glycolide was polymerized in bulk at 160 °C using various metal acetylacetonates as catalysts. Zirconium acetylacetonate was particularly efficient, enabling rapid polymerization even at 130 °C. The formation of cyclic poly(glycolic acid) (PGA), most likely via a ring-expansion polymerization (REP) mechanism, was proven by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Depending on the polymerization conditions, the formation of even-numbered cycles was favored to varying degrees. Number-average molecular weights (Mn) in the range of 2000–3500 g mol−1 were achieved with dispersities below 2.0. Wide-angle X-ray scattering (WAXS) powder patterns showed that the crystal lattice was the same as that of known linear PGAs, regardless of the Mn values. These patterns enabled a comparison of crystallinities with values derived from DSC measurements.
KW - MALDI-TOF MS
KW - Polyglycolide
KW - Crystallization
KW - Small-angle X-ray scattering
KW - Cyclization
PY - 2026
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-653731
DO - https://doi.org/10.1039/d5ra07961f
SN - 2046-2069
VL - 16
IS - 2
SP - 1757
EP - 1764
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-65373
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - El Malah, T.
A1 - Ciesielski, A.
A1 - Piot, L.
A1 - Troyanov, S.I.
A1 - Mueller, U.
A1 - Weidner, Steffen
A1 - Samorì, P.
A1 - Hecht, S.
T1 - Conformationally pre-organized and pH-responsive flat dendrons: Synthesis and self-assembly at the liquid-solid interface
N2 - Efficient Cu-catalyzed 1,3-dipolar cycloaddition reactions have been used to prepare two series of three regioisomers of G-1 and G-2 poly(triazole-pyridine) dendrons. The G-1 and G-2 dendrons consist of branched yet conformationally pre-organized 2,6-bis(phenyl/pyridyl-1,2,3-triazol-4-yl)pyridine (BPTP) monomeric and trimeric cores, respectively, carrying one focal and either two or four peripheral alkyl side chains. In the solid state, the conformation and supramolecular organization were studied by means of a single crystal X-ray structure analysis of one derivative. At the liquid-solid interface, the self-assembly behavior was investigated by scanning tunneling microscopy (STM) on graphite surfaces. Based on the observed supramolecular organization, it appears that the subtle balance between conformational preferences inherent in the dendritic backbone on the one side and the adsorption and packing of the alkyl side chains on the graphite substrate on the other side dictate the overall structure formation in 2D.
KW - Dendrons
KW - Scanning tunneling microscopy (STM)
KW - Single crystal X-ray structure analysis
PY - 2012
DO - https://doi.org/10.1039/c1nr11434d
SN - 2040-3364
SN - 2040-3372
VL - 4
SP - 467
EP - 472
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-25378
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zhao, J.
A1 - Schlaad, H.
A1 - Weidner, Steffen
A1 - Antonietti, M.
T1 - Synthesis of terpene-poly(ethylene oxide)s by t-BuP4-promoted anionic ring-opening polymerization
N2 - Terpene alcohols (menthol, retinol, cholesterol, and betulin) together with the phosphazene base t-BuP4 were used as initiating systems for anionic ring-opening polymerization of ethylene oxide. The polymerizations were conducted in a controlled manner with the initial molar ratio of t-BuP4 to hydroxyl groups of 0.01–0.2, yielding a series of biohybrid polymers comprising terpene entities and poly(ethylene oxide) (PEO) chains with low polydispersities and tunable compositions (57–87 wt% of PEO). Samples were characterized by NMR and UV/visible spectroscopy, MALDI-TOF mass spectrometry, and size exclusion chromatography; thermal properties were studied by differential scanning calorimetry. The concept of this study opens a new toolbox of terpene-based biohybrid polymers with variable properties and functions.
KW - ROMP
KW - MALDI
KW - Amphiphilic polymers
KW - Polyethylene oxide
PY - 2012
DO - https://doi.org/10.1039/c1py00388g
SN - 1759-9954
SN - 1759-9962
VL - 3
IS - 7
SP - 1763
EP - 1768
PB - Royal Society of Chemistry (RSC)
CY - Cambridge
AN - OPUS4-26026
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Enthaler, S.
A1 - Krackl, S.
A1 - Epping, J. D.
A1 - Eckhardt, B.
A1 - Weidner, Steffen
A1 - Fischer, A.
T1 - Iron-based pre-catalyst supported on polyformamidine for C-C bond formation
N2 - In the present study the incorporation of iron into an organic polymer, composed of formamidine subunits [R–N=C(H)–NH–R], has been examined. The catalytic ability of the recyclable material was investigated in the iron-catalyzed formation of C–C bonds. After optimization of the reaction conditions, excellent yields and chemoselectivities were feasible.
KW - Polyforamidine
KW - Synthesis
KW - Catalytic ability
PY - 2012
DO - https://doi.org/10.1039/c2py00540a
SN - 1759-9954
SN - 1759-9962
VL - 3
IS - 3
SP - 751
EP - 756
PB - Royal Society of Chemistry (RSC)
CY - Cambridge
AN - OPUS4-25461
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Fandrich, Nick
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
A1 - Staal, B.
A1 - Thünemann, Andreas
A1 - Laschewsky, A.
T1 - Characterization of new amphiphilic block copolymers of N-vinylpyrrolidone and vinyl acetate, 2 - chromatographic separation and analysis by MALDI-TOF and FT-IR coupling
N2 - PVP-block-PVAc block copolymers were synthesized by controlled radical polymerization applying a RAFT/MADIX system and were investigated by HPLC and by coupling of chromatography to FT-IR spectroscopy and MALDI-TOF MS. Chromatographic methods (LACCC and gradient techniques) were developed that allowed a separation of block copolymers according to their repeating units. The results of the spectroscopic and spectrometric analysis clearly showed transfer between radicals and process solvent. With the use of hyphenated techniques differences between main and side products were detected. In agreement with previously published results, obtained by NMR, SEC, static light scattering and MALDI-TOF MS, our data proved a non-ideal RAFT polymerization.
KW - Amphiphiles
KW - Block copolymers
KW - Liquid chromatography
KW - MALDI
KW - Reversible addition fragmentation chain transfer (RAFT)
KW - Liquid adsorption chromatography at critical conditions
KW - Gradient chromatography
KW - MALDI-TOF mass spectrometry
KW - Hyphenated techniques
KW - Mechanism of polymerization
PY - 2010
DO - https://doi.org/10.1002/macp.201000044
SN - 1022-1352
SN - 1521-3935
VL - 211
IS - 15
SP - 1678
EP - 1688
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-22012
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Just, Ulrich
A1 - Werthmann, Barbara
A1 - Decker, Renate
A1 - Schwarz, Bärbel
A1 - Borowski, Renate
T1 - MALDI/MS - A New Technique in Characterizing Chemical Heterogeneity of Degradation Products of Poly(Ethylene Terephthalate)s
T2 - International GPC Symposium '96
CY - San Diego, CA, USA
DA - 1996-09-08
PY - 1996
SP - 632
EP - 651
CY - Milford, Mass.
AN - OPUS4-11905
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Friedrich, Jörg Florian
T1 - Infrared-Matrix-assisted Laser Desorption/Ionization and Infrared-Laser Desorption/Ionization Investigations of Synthetic Polymers
PY - 1998
SN - 0951-4198
SN - 1097-0231
VL - 12
SP - 1373
EP - 1381
PB - Wiley
CY - Chichester
AN - OPUS4-6988
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Wolff, D.
A1 - Springer, J.
T1 - Influence of Chirality on Phase Behaviour of Copolymers Containing Cholesterol as Mesogenic Group
PY - 1996
SN - 1022-1352
SN - 1521-3935
VL - 197
SP - 1337
EP - 1348
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-11091
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Just, Ulrich
A1 - Werthmann, Barbara
A1 - Weidner, Steffen
T1 - Referenzmaterialien für die Polymeranalytik - Verfahren zur Charakterisierung und Bewertung
PY - 1998
SN - 0943-6677
VL - 49
IS - 6
SP - 223
EP - 228
PB - Rubikon
CY - Gaiberg bei Heidelberg
AN - OPUS4-11261
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Böhmert, L.
A1 - Girod, Matthias
A1 - Hansen, Ulf
A1 - Maul, Ronald
A1 - Knappe, Patrick
A1 - Niemann, B.
A1 - Weidner, Steffen
A1 - Thünemann, Andreas
A1 - Lampen, A.
T1 - Analytically monitored digestion of silver nanoparticles and their toxicity on human intestinal cells
N2 - Orally ingested nanoparticles may overcome the gastrointestinal barrier, reach the circulatory system, be distributed in the organism and cause adverse health effects. However, ingested nanoparticles have to pass through different physicochemical environments, which may alter their properties before they reach the intestinal cells. In this study, silver nanoparticles are characterised physicochemically during the course of artificial digestion to simulate the biochemical processes occurring during digestion. Their cytotoxicity on intestinal cells was investigated using the Caco-2 cell model. Using field-flow fractionation combined with dynamic light scattering and small-angle X-ray scattering, the authors found that particles only partially aggregate as a result of the digestive process. Cell viabilities were determined by means of CellTiter-Blue® assay, 4',6-diamidino-2-phenylindole-staining and real-time impedance. These measurements reveal small differences between digested and undigested particles (1–100 µg/ml or 1–69 particles/cell). The findings suggest that silver nanoparticles may indeed overcome the gastrointestinal juices in their particulate form without forming large quantities of aggregates. Consequently, the authors presume that the particles can reach the intestinal epithelial cells after ingestion with only a slight reduction in their cytotoxic potential. The study indicates that it is important to determine the impact of body fluids on the nanoparticles of interest to provide a reliable interpretation of their nano-specific cytotoxicity testing in vivo and in vitro.
KW - Silver nanoparticles
KW - In vitro digestion
KW - Field-flow fractionation
KW - Small-angle X-ray scattering
KW - Dynamic light scattering
KW - Caco-2 cells
PY - 2014
DO - https://doi.org/10.3109/17435390.2013.815284
SN - 1743-5390
SN - 1743-5404
VL - 8
IS - 6
SP - 631
EP - 642
PB - Informa Healthcare
CY - London
AN - OPUS4-29926
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Cyclic poly(L-lactide)s via ring-expansion polymerizations catalysed by 2,2-dibutyl-2- stanna-1,3-dithiolane
N2 - L-Lactides were polymerized in bulk at 120 or 160 °C with cyclic dibutyltin catalysts derived from 1,2-dimercaptoethane or 2-mercaptoethanol. Only linear chains having one benzyl ester and one OH-end group were obtained when benzyl alcohol was added. When L-lactides were polymerized with neat dibutyl-2-stanna-1,3-dithiolane, exclusively cyclic polylactides were formed even at 120 °C. The temperature, time and monomer/catalyst ratio (M/C) were varied. These results are best explained by a combination of ring-expansion polymerization and ring-extrusion of cyclic oligo- or polylactides with Elimination of the cyclic catalyst. Neither syntheses of linear polylactides nor of cyclic lactides involved racemization up to 20 h at 160 °C.
KW - Ring-expansion polymerization
KW - MALDI
KW - Polylactides
PY - 2017
DO - https://doi.org/10.1039/C6PY02166B
SN - 1759-9954
SN - 1759-9962
VL - 8
IS - 9
SP - 1589
EP - 1596
PB - Royal Society of Chemistry
AN - OPUS4-39748
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Wachtendorf, Volker
A1 - Geburtig, Anja
A1 - Elert, Anna Maria
A1 - Weidner, Steffen
T1 - Einfluss von Feuchte und Nässe auf die Witterungs-induzierte Alterung am Beispiel eines Polyurethans
N2 - In diesem Beitrag soll der relative Einfluss des Wassers als Feuchte und Nässe unter den Beanspruchungsfaktoren untersucht werden. Die Unterscheidung von Luftfeuchte und Nässe bezüglich ihrer Wirkung ist dabei notwendig, weil die stehende Nässe zusätzliche Extraktionswirkung besitzt und auch die verfügbare Sauerstoffmenge beeinflusst.
Dazu wurde ein Polymer, das im Rahmen des BAM-internen Projektes PolyComp untersucht wird, künstlich bewittert. Hierzu wurde ein Fluoreszenzlampengerät mit UV-A 340 nm Leuchtstoffröhren verwendet, in dessen Probenraum durch zusätzliche Kammern die gleichzeitige Bewitterung unter drei unterschiedlichen Feuchte-Varianten realisiert wurde (bei konstanter Temperatur):
- UV und trocken
- UV und hohe Luftfeuchte
- UV und stehende Nässe
Das gleichzeitige Einwirken der einzelnen Einflussfaktoren kann dabei konkurrierende oder aufeinander folgende chemische Reaktionen und physikalische Prozesse und somit ein anderes Ergebnis bewirken, als wenn sie isoliert nacheinander auf eine Probe eingewirkt hätten.
Über die erwähnten Varianten hinaus kann auch noch der spezifische Einfluss der UV-Strahlung mit untersucht werden, weil die Proben im Bereich ihrer Befestigung verdeckt sind.
Die Methodik und erste Ergebnisse dieser Untersuchung werden präsentiert.
T2 - 46. Jahrestagung der Gesellschaft für Umweltsimulation (GUS) 2017
CY - Stutensee-Blankenloch bei Karlsruhe, Germany
DA - 22.03.2017
KW - Polyurethan
KW - TPU
KW - Bewitterung
KW - UV
KW - Feuchte
KW - Nässe
PY - 2017
SN - 978-3-9816286-9-2
VL - 46
SP - 251
EP - 261
PB - Gesellschaft für Umweltsimulation e. V
CY - Pfinztal (Berghausen)
AN - OPUS4-39906
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Theiler, Geraldine
A1 - Wachtendorf, Volker
A1 - Elert, Anna Maria
A1 - Weidner, Steffen
T1 - Effects of UV radiation on the friction behavior of thermoplastic polyurethanes
N2 - The effects of weathering exposure on unfilled and filled thermoplastic polyurethanes (TPU) materials are described as performed under different humidity conditions. For this purpose, a weathering device was used with UV-A 340 nm lamps at a constant temperature of 40 °C. The effects of environmental (UV and humidity condition) degradation on the frictional properties of TPU materials are presented along with surface analyses to characterize the chemistry of the degradative process. Photooxidative degradation of unfilled polymer leads to deterioration of physical and mechanical properties, which affects its tribological behavior significantly. Due to crosslinking, the stiffness of the material increases, reducing drastically the friction coefficient of unfilled TPUs. The frictional behavior of glass fiber reinforced TPU is less affected by radiation.
KW - Photooxidation
KW - UV radiation
KW - Friction
KW - TPU
KW - Humidity
PY - 2018
DO - https://doi.org/10.1016/j.polymertesting.2018.08.006
SN - 0142-9418
SN - 1873-2348
VL - 70
SP - 467
EP - 473
PB - Elsevier Ltd.
CY - Amsterdam
AN - OPUS4-45709
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF MS in der Synthese hochmolekularer Polylaktid Homo- und Copolymere
N2 - Die MALDI-TOF Massenspektrometrie stellt eine wichtige Methode zur simultanen Bestimmung von Molmassen, Molmassenverteilungen und Endgruppen von synthetischen Polymeren dar. In dem Vortrag wird gezeigt, welche zusätzlichen Informationen über die Art der Polymerisation, der Nebenreaktionen und der Topologie der gebildeten hochmolekularen Polylaktid-Homo- und Copolymere im Verlauf ihrer Synthese erhalten werden können.
T2 - Bruker Anwendertreffen
CY - Online meeting
DA - 05.03.2021
KW - MALDI
KW - Polylaktide
PY - 2021
AN - OPUS4-52278
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Just, Ulrich
A1 - Weidner, Steffen
A1 - Wittke, Wolfgang
A1 - Friedrich, Jörg Florian
A1 - Rittig, F.
A1 - Gruber, F.
T1 - 2D-Characterization of Polyamides using Chromatography and MALDI-TOF-MS
T2 - Waters International GPC 2003 and ISPAC-16-Symposium
CY - Baltimore, MD, USA
DA - 2003-06-09
PY - 2003
AN - OPUS4-2631
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - UV- und IR-MALDI-TOF-MS zur Bestimmung von Molmasse und chemischer Heterogenität von synthetischen Polymeren
T2 - 4. Deutsches Bruker Daltonik MALDI-TOF-MS Anwendertreffen
CY - Fulda, Germany
DA - 1999-04-15
PY - 1999
AN - OPUS4-11282
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI - Untersuchung zur Oberflächenmodifizierung von Polymeren nach Plasmabehandlung
T2 - 4. MALDI-Anwendertreffen (Shimadzu)
CY - Duisburg, Germany
DA - 1997-11-26
PY - 1997
AN - OPUS4-11280
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - You, Zengchao
A1 - Nirmalananthan-Budau, Nithiya
A1 - Resch-Genger, Ute
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Separation of polystyrene nanoparticles bearing different carboxyl group densities and functional groups quantification with capillary electrophoresis and asymmetrical flow field flow fractionation
N2 - Two sets of polystyrene nanoparticles (PSNPs) with comparable core sizes but different carboxyl group densities were made and separated using asymmetric flow field flow fractionation (AF4), capillary electrophoresis (CE), and the off-line hyphenation of both methods. Our results revealed the significant potential of two-dimensional off-line AF4-CE hyphenation to improve the separation and demonstrated for the first time, the applicability of CE to determine the functional group density of nanoparticles (NPs). Compared to the result acquired with conductometric titration, the result obtained with synthesized 100 nm sized PSNPs revealed only a slight deviation of 1.7%. Commercial 100 nm sized PSNPs yielded a deviation of 4.6 %. For 60 nm sized PSNPs, a larger deviation of 10.6 % between both methods was observed, which is attributed to the lower separation resolution.
KW - Nanoparticle
KW - A4F
KW - Capillary electrophoresis
KW - Carboxyl group
PY - 2020
DO - https://doi.org/10.1016/j.chroma.2020.461392
VL - 1626
SP - 461392
PB - Elsevier B.V.
AN - OPUS4-51080
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H. R.
T1 - Sn(II)2-ethylhexanoate-catalyzed polymerizations of L-lactide in solution – Solution grown crystals of cyclic Poly(L-Lactide)s
N2 - L-lactide (LA) was polymerized in toluene by means of neat tin(II) 2-ethylhexanoate (SnOct2). Concentration, time and temperature were varied. The isothermally crystallized polyLAs (PLA) were characterized in the virgin state with regard to topology, molar mass, melting temperature (Tm), crystal modification, high or low Tm morphology, crystallinity and crystal thickness. Even a small amount of solvent favored cyclization relative to polymerization in bulk, so that cyclic polylactides were obtained at 115 ◦C and even at 95 ◦C. At all temperatures the α-modification of PLA was obtained along with crystallinities up to 90%. With 6 M solution the high Tm morphology with Tm’s > 190 ◦C was obtained at 115 ◦C. The crystal thickness of crystallites grown from solution at 115 ◦C was on the average 10–20% higher than that of PLA polymerized in bulk. At a polymerization temperature of 75 ◦C cyclization was incomplete and fewer perfect crystallites were formed. A new hypothesis for the crystal growth of cyclic polyLAs is proposed.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
KW - Polymerization
PY - 2022
DO - https://doi.org/10.1016/j.polymer.2022.125142
SN - 0032-3861
VL - 255
SP - 1
EP - 9
PB - Elsevier
CY - Oxford
AN - OPUS4-55283
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Hoskins, Jessica
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
ED - Udomkichdecha, W.
ED - Böllinghaus, Thomas
ED - Manonukul, A.
ED - Lexow, J.
T1 - Characterization of randomly branched polymers utilizing liquid chromatography and mass spectrometry
N2 - Branching in polymers is an important way to modify the materials properties, however the characterization of random branching in polymeric materials is a challenge in polymer analysis. In this work, liquid adsorption chromatography methods are developed for a commercially available hyperbranched polyester (Boltorn™). This Chromatographie techniques was then coupled to offline MALDI-TOF MS analysis, a first in the analysis of randomly branched polymers. The coupling of these two techniques provides superior MALDI-TOF spectra, enabling the easy identification of structural subdistributons based on theoretical molecular weight. Detailed analysis of the MALDI-TOF spectra shows that these Chromatographie conditions separate cyclic Boltorn polymers (with no core molecule) from non-cyclic polymers (with core molecule), and these are the only two architectures observed. MALDI MS also confirms that the Chromatographie Separation mode is adsorption, but further analysis is needed to determine if there is a Separation by degree of branching.
KW - Hyperbranched polyesters
KW - Polymer mass spectrometry
KW - Polymer chromatography
KW - Liquid adsorption chromatography
KW - MALDI-TOF MS
KW - Carbon capture
KW - Climate change
KW - Lubricant
KW - Micro manufacturing
KW - Multiphysics simulations
KW - WMRIF
PY - 2014
SN - 978-3-319-11339-5
SN - 978-3-319-11340-1
SP - 1
EP - 10
PB - Springer
AN - OPUS4-32519
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Geng, Sh.
A1 - Koprinarov, Ivaylo
A1 - Kühn, Gerhard
A1 - Weidner, Steffen
T1 - Modelling plasma-induced reactions on polymer surfaces using aliphatic self-assembling and LB layers
PY - 1998
SN - 0257-8972
VL - 98
SP - 1132
EP - 1141
PB - Elsevier Science
CY - Lausanne
AN - OPUS4-6999
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Trimpin, s.
T1 - Mass Spectrometry of Synthetic Polymers
KW - Polymere
KW - Massenspektrometrie
KW - MALDI
PY - 2010
DO - https://doi.org/10.1021/ac101080n
SN - 0003-2700
SN - 1520-6882
VL - 82
IS - 12
SP - 4811
EP - 4829
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-21623
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Trimpin, Sarah
A1 - Yenchick, Frank S.
A1 - Lee, Chuping
A1 - Hoang, Khoa
A1 - Pophristic, Milan
A1 - Karki, Santosh
A1 - Marshall, Darrell D.
A1 - Lu, I-Chung
A1 - Lutomski, Corinne A.
A1 - El-Baba, Tarick J.
A1 - Wang, Beixi
A1 - Pagnotti, Vincent S.
A1 - Meher, Anil K.
A1 - Chakrabarty, Shubhashis
A1 - Imperial, Lorelei F.
A1 - Madarshahian, Sara
A1 - Richards, Alicia L.
A1 - Lietz, Christopher B.
A1 - Moreno-Pedraza, Abigail
A1 - Leach, Samantha M.
A1 - Gibson, Stephen C.
A1 - Elia, Efstathios A.
A1 - Thawoos, Shameemah M.
A1 - Woodall, Daniel W.
A1 - Jarois, Dean R.
A1 - Davis, Eric T.J.
A1 - Liao, Guochao
A1 - Muthunayake, Nisansala S.
A1 - Redding, McKenna J.
A1 - Reynolds, Christian A.
A1 - Anthony, Thilani M.
A1 - Vithanarachchi, Sashiprabha M.
A1 - DeMent, Paul
A1 - Adewale, Adeleye O.
A1 - Yan, Lu
A1 - Wager-Miller, James
A1 - Ahn, Young-Hoon
A1 - Sanderson, Thomas H.
A1 - Przyklenk, Karin
A1 - Greenberg, Miriam L.
A1 - Suits, Arthur G.
A1 - Allen, Matthew J.
A1 - Narayan, Srinivas B.
A1 - Caruso, Joseph A.
A1 - Stemmer, Paul M.
A1 - Nguyen, Hien M.
A1 - Weidner, Steffen
A1 - Rackers, Kevin J.
A1 - Djuric, Ana
A1 - Shulaev, Vladimir
A1 - Hendrickson, Tamara L.
A1 - Chow, Christine S.
A1 - Pflum, Mary Kay H.
A1 - Grayson, Scott M.
A1 - Lobodin, Vladislav V.
A1 - Guo, Zhongwu
A1 - Ni, Chi-Kung
A1 - Walker, J. Michael
A1 - Mackie, Ken
A1 - Inutan, Ellen D.
A1 - McEwen, Charles N.
T1 - New Processes for Ionizing Nonvolatile Compounds in Mass Spectrometry: The Road of Discovery to Current State-of-the-Art
N2 - This Perspective covers discovery and mechanistic aspects aswell as initial applications of novel ionization processes for use in massspectrometry that guided us in a series of subsequent discoveries, instrumentdevelopments, and commercialization. Vacuum matrix-assisted ionization onan intermediate pressure matrix-assisted laser desorption/ionization sourcewithout the use of a laser, high voltages, or any other added energy wassimply unbelievable, at first. Individually and as a whole, the variousdiscoveries and inventions started to paint, inter alia, an exciting new pictureand outlook in mass spectrometry from which key developments grew thatwere at the time unimaginable, and continue to surprise us in its simplisticpreeminence. We, and others, have demonstrated exceptional analyticalutility. Our current research is focused on how best to understand, improve, and use these novel ionization processes throughdedicated platforms and source developments. These ionization processes convert volatile and nonvolatile compounds from solid orliquid matrixes into gas-phase ions for analysis by mass spectrometry using, e.g., mass-selected fragmentation and ion mobilityspectrometry to provide accurate, and sometimes improved, mass and drift time resolution. The combination of research anddiscoveries demonstrated multiple advantages of the new ionization processes and established the basis of the successes that lead tothe Biemann Medal and this Perspective. How the new ionization processes relate to traditional ionization is also presented, as wellas how these technologies can be utilized in tandem through instrument modification and implementation to increase coverage ofcomplex materials through complementary strengths.
KW - Mass spectrometry
PY - 2024
DO - https://doi.org/10.1021/jasms.3c00122
SN - 1879-1123
VL - 35
IS - 12
SP - 2753
EP - 2784
PB - American Chemical Society (ACS)
AN - OPUS4-61417
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Scholz, Philipp
A1 - Wachtendorf, Volker
A1 - Elert, Anna Maria
A1 - Falkenhagen, Jana
A1 - Becker, Roland
A1 - Hoffmann, Katrin
A1 - Resch-Genger, Ute
A1 - Tschiche, Harald
A1 - Reinsch, Stefan
A1 - Weidner, Steffen
ED - Scholz, Philipp
T1 - Analytical toolset to characterize polyurethanes after exposure to artificial weathering under systematically varied moisture conditions
N2 - Polyether and -ester urethanes (PU) were exposed to artificial weathering at 40 °C and artificial UV radiation in a weathering chamber. In 3 parallel exposures, humidity was varied between dry, humid, and wet conditions. Material alteration was investigated by various analytical techniques like size exclusion chromatography
(SEC), liquid chromatography-infrared spectroscopy (LC-FTIR), thermal-desorption gas chromatography-mass spectrometry (TD-GC-MS), fluorescence mapping and dynamic mechanical analysis (DMA). Our results show that depending on the weathering conditions, different degradation effects can be observed. By means of SEC an initial strong decrease of the molar masses and a broadening of the mass distributions was found. After a material dependent time span this was followed by a plateau where molar mass changes were less significant. A minor moisture-dependent degradation effect was only found for polyester PU. Fluorescence measurements on two materials revealed an increase in the luminescence intensity upon weathering process reaching a saturation level after about 500 h. The changes in the optical properties observed after different exposure conditions and times were very similar. The TD-GC-MS data showed the fate of the stabilizers and antioxidant in the course of weathering. LC-FTIR measurements revealed a change in peak intensities and the ratio of urethane and carbonyl bands.
KW - Polyurethane
KW - Artificial weathering
KW - Moisture
KW - Crosslinking
KW - Degradation
PY - 2019
UR - https://www.sciencedirect.com/science/article/pii/S0142941819303708
DO - https://doi.org/10.1016/j.polymertesting.2019.105996
SN - 0142-9418
VL - 78
SP - 105996, 1
EP - 9
PB - Elsevier
CY - Amsterdam
AN - OPUS4-48625
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.R.
A1 - Mix, Renate
A1 - Weidner, Steffen
T1 - Poly(ester urethane)s derived from lactide, isosorbide, terephthalic acidm abd various diisocyanates
N2 - Isosorbide-initiated oligomerizations of ʟ-lactide were preformed in bulk using SnCl2 as catalyst. The resulting telechelic OH-terminated oligoesters were in situ subjected to simultaneous polycondensation and polyaddition with mixtures of terephthaloyl chloride and diisocyanates. Most polymerizations were conducted with 4,4'-diisocyanatodiphenyl methane and 2,4-diisocyanato toluene. The consequences of excess diisocyanate and four different catalysts were studied. The isosorbide/lactide ratio and the terephthalic acid/diisocyanate ratio were varied. Number average molecular weights up to 15 kDa with polydispersities around 3–5 were obtained. Depending on the chemical structure of the copolyester and on the feed ratio, incorporation of urethane groups may reduce or enhance the glass-transition temperature, but the thermal stability decreases dramatically regardless of composition.
KW - Cyclization
KW - Isosorbide
KW - Lactide
KW - Polyaddition
KW - Polycondensation
KW - Polyesters
KW - Polyurethanes
PY - 2014
DO - https://doi.org/10.1002/pola.27069
SN - 0360-6376
SN - 0887-624X
VL - 52
IS - 6
SP - 867
EP - 875
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-30299
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gonzalez-Rojano, N.
A1 - Arias-Marin, E.
A1 - Navarro-Rodriguez, D.
A1 - Weidner, Steffen
T1 - Bidirectional Synthesis of a Series of 2,5- Dodecanoy-phenylene-ethynylene oligomers
N2 - A family of rigid rod like 2,5-dodecanoxy-phenyleneethynylene oligomers having 3, 5, 7, and 9 repeating units was selectively synthesized by a bi-directional iterative divergent-convergent approach. Starting from a central 1,4-bis(dodecanoxy)-2,5-diiodobenzene monomer, only two repetitive reactions were involved with each cycle of oligomerization: a Pd/Cu cross-coupling with the bifunctional monomer 1-(3,3-diethyltriazene)-2,5-bis(dodecanoxy)-4-(ethynyl)benzene, generating oligomers with terminal triazene groups, followed by a further nucleophilic substitution with iodine.
KW - Conjugated oligomers
KW - Phenyleneethynylenes
KW - Triazenes
KW - Aryl iodides
KW - Sonoga
PY - 2005
DO - https://doi.org/10.1055/s-2005-868474
SN - 0936-5214
SN - 1437-2096
IS - 8
SP - 1259
EP - 1262
PB - Thieme
CY - Stuttgart
AN - OPUS4-11100
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kona, Balakantha Rao
A1 - Weidner, Steffen
A1 - Friedrich, Jörg Florian
T1 - Epoxidation of Polydienes Investigated by MALDI-TOF Mass Spectrometry and GPC-MALDI Coupling
N2 - Polybutadienes (PB) and polyisoprenes (PI) with various molecular weights and polydispersities were epoxidized applying two different synthetic routes. The degree of epoxidation was determined by means of matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). It has been found that the degree of functionalization of polybutadiene is generally lower than that for polyisoprenes. Additionally, PB shows lower degrees of epoxidation at higher masses, whereas the level of functionalization of PI was unaffected by the molar mass. Coupling of gel permeation chromatography (GPC) with MALDI-TOF mass spectrometry was successfully used for the investigation of epoxidized polymers with higher masses. Using mass spectra of single fractions, the degree of epoxidation could be determined and applied for a calibration of GPC.
PY - 2005
DO - https://doi.org/10.1080/10236660490935736
SN - 1023-666X
SN - 1563-5341
VL - 10
IS - 1-2
SP - 85
EP - 109
PB - Gordon and Breach Publ.
CY - Amsterdam
AN - OPUS4-11860
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Garaleh, M.
A1 - Kricheldorf, H.R.
A1 - Weidner, Steffen
A1 - Yashiro, T.
T1 - Hafnium chloride catalyzed polycondensation of Alpha, Omega-alkanediol with dicarboxylic acids or succinic anhydride
KW - Polyester
KW - Polycondensation
KW - Hafnium
KW - Cyclization
PY - 2010
DO - https://doi.org/10.1080/10601320903539199
SN - 1060-1325
SN - 1520-5738
VL - 47
IS - 4
SP - 303
EP - 308
PB - Taylor & Francis
CY - Philadelphia, PA
AN - OPUS4-22953
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Scheliga, F.
A1 - Kricheldorf, H.R.
T1 - Low-temperature polymerization of epsilon-caprolactone catalyzed by cerium triflates
N2 - Using 22 metal triflates as catalysts, ε-caprolactone is polymerized at 22 °C in bulk. Only five relatively acidic triflates prove active. Three triflates, including the neutral Sm3+, are active using water as initiator. A very low content of cyclics is found in all the experiments. With Ce3+ and Ce4+, polymerizations are performed in CH2Cl2 and in bulk at 2 °C and 22 °C. Low dispersities (down to 1.1) are obtained. At 22 °C, Ce4+ and, even better, Ce3+ also catalyze syntheses of CO2H- and CH2OH-terminated polycaprolactones, whereby higher dispersities and larger fractions of cyclics are obtained. Further polymerizations and polycondensations are catalyzed with protic acids. The results can be explained by a proton-catalyzed activated monomer mechanism.
KW - Epsilon-caprolactone
KW - Cyclization
KW - Metal triflates
KW - Polycondensation
KW - Ring-opening polymerization
PY - 2013
DO - https://doi.org/10.1002/macp.201300279
SN - 1022-1352
SN - 1521-3935
VL - 214
IS - 18
SP - 2043
EP - 2053
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-29219
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Multivariate statistics applied to MALDI-TOF MS data of pollen samples
N2 - Pollen represent one major cause for human allergic diseases. Currently the characterization and identification of pollen is time-consuming since it mainly relies on the microscopic determination of the genus-specific pollen morphology. A variety of new analytical approaches, like Raman - and fluorescence spectroscopy have been proposed in order to develop fast and reliable pollen identification. Recently matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was initially applied for the rapid investigation of such complex biological samples. Taxonomic differences and relations of single pollen grains could be identified.
Both commercially available lyophilized pollen and fresh pollen acquired from biological samples collected in parks and in the Botanical Garden Berlin in the years 2013-2015 were investigated. The samples were prepared by formic acid extraction in the gas phase and spotted with HCCA matrix. A variety of new approaches, like a newly developed MALDI target with micrometer sample spots sizes, were tested for their suitability. The obtained mass spectral data were investigated by principal component analysis (PCA).
The applicability of MALDI-TOF mass spectrometry for the classification of pollen according to their taxonomic relationships was proven. Specifically, chemical differences in the mass spectra at the levels of plant order, genus and in many cases even of species could be identified. Based on these results, further investigations have been undertaken to optimize the sample preparation for the classification of single pollen grains in mixtures of pollens. A novel MALDI-target design was developed to enhance the phenotypic information of pollens in their mass spectra. The combination of mass spectral patterns and multivariate statistics provide a powerful tool for the investigation of structural correlations within mixtures. The results can be used to improve the reconstruction of taxonomic relations of single species in various mixtures and might be useful for the development of a fast routine method to identify pollen based on mass spectrometry.
T2 - 64th ASMS Conference on Mass Spectrometry and Allied Topics
CY - San Antonio, TX, USA
DA - 05.06.2016
KW - Pollen
KW - MALDI-TOF Mass Spectrometry
KW - Multivariate statistics
PY - 2016
AN - OPUS4-36837
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Koprinarov, Ivaylo
A1 - Kühn, Gerhard
A1 - Weidner, Steffen
A1 - Vogel, Lydia
T1 - Chemical reactions at polymer surfaces interacting with a gas plasma or with metal atoms - their relevance to adhesion
N2 - The chemical and morphological stabilities of polymer segments in the near-surface layer were investigated by spectroscopic methods such as X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. Model studies were undertaken with LangmuirBlodgett films, self-assembled monolayers and oligomer films. For thin polymer layers (30 to 500 nm), the changes in molecular-weight distributions of some polymers were investigated systematically by size exclusion chromatography, matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry and thermal-field flow fractionation for oxygen- and helium-plasma exposures. The polymer surfaces were found to be relatively stable at exposure to an oxygen low-pressure plasma up to ca. 2 s. This is important information to get maximum adhesion to metals in composites. In correlation to their redox potentials, potassium, aluminium and chromium react with oxygen functional groups at the polymer/metal interface. In a dedicated study, chromium was found to attack aromatic rings and form different reaction products.
PY - 1999
DO - https://doi.org/10.1016/S0257-8972(99)00229-7
SN - 0257-8972
VL - 116-119
SP - 772
EP - 782
PB - Elsevier Science
CY - Lausanne
AN - OPUS4-6981
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Knop, K.
A1 - Thünemann, Andreas
T1 - Structure and end-group analysis of complex hexanediol-neopentylglycol-adipic acid copolyesters by matrix-assisted laser desorption/ionization collision-induced dissociation tandem mass spectrometry
N2 - Sequences and end groups of complex copolyesters were determined by fragmentation analysis by means of matrix-assisted laser desorption/ionization collision-induced dissociation tandem mass spectrometry (MALDI CID MS/MS). The complexity of the crude copolyester mixture was reduced by a chromatographic separation followed by a MALDI time-of-flight (TOF) investigation of fractions. Due to overlapping compositional and end-group information a clear assignment of end groups was very difficult. However, the fragmentation of suitable precursor ions resulted in typical fragment ion patterns and, therefore, enabled a fast and unambiguous determination of the end groups and composition of this important class of polymers.
KW - Fragmentierung
KW - MALDI Massenspektrometrie
KW - Polymere
KW - MS/MS
PY - 2009
DO - https://doi.org/10.1002/rcm.4191
SN - 0951-4198
SN - 1097-0231
VL - 23
IS - 17
SP - 2768
EP - 2774
PB - Wiley
CY - Chichester
AN - OPUS4-20929
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Roessner, D.
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
ED - Olefjord, I.
ED - Nyborg, L.
ED - Briggs, D.
T1 - Changes in molecular weight distribution of polymers by plasma treatment
T2 - 7th European Conference on Applications of Surface and Interface Analysis
CY - Göteborg, Sweden
DA - 1997-06-16
PY - 1997
SN - 0-471-97827-2
SP - 795
EP - 799
PB - Wiley
CY - Chichester
AN - OPUS4-6997
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MassChrom2D - a software that combines chromatographic separation and mass spectrometric identification to analyze the composition of copolymers
T2 - 60th ASMS Conference on Mass Spectrometry and Allied Topics
CY - Vancouver, Canada
DA - 2012-05-20
PY - 2012
AN - OPUS4-25954
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Friedrich, Jörg Florian
A1 - Kühn, Gerhard
A1 - Mix, Renate
A1 - Retzko, Iris
A1 - Gerstung, Vanessa
A1 - Weidner, Steffen
A1 - Schulze, Rolf-Dieter
A1 - Unger, Wolfgang
ED - Mittal, K. L.
T1 - Plasma polymer adhesion promoters for metal-polymer systems
T2 - 2nd International Symposium on Polyimides and Other High Temperature Polymers: Synthesis, Characterization and Applications
CY - Newark, NJ, USA
DA - 2001-12-03
KW - r.f. pulsed plasma
KW - Plasma polymers with functional groups
KW - Copolymers
KW - Adhesion promoting interlayers
KW - Metal-polymer systems
PY - 2003
SN - 90-6764-378-5
VL - 2
SP - 359
EP - 388
PB - VSP
CY - Utrecht
AN - OPUS4-6967
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-MS - supplementary to chromatographic techniques in characterizing chemical heterogeneity of oligomer ethylene terephthalates
T2 - GdCH - Jahrestagung (Arbeitskreis Chromatographie)
CY - Leipzig, Germany
DA - 1995-11-06
PY - 1995
AN - OPUS4-11119
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF Massenspektrometrie von Polymeren - Anwendungen, Probleme, Trends
T2 - Kolloquium zum Thema "Untersuchungen von synthetischen bzw. Biopolymeren mit MALDI-TOF-MS"
CY - Dresden, Germany
DA - 2009-12-10
PY - 2009
AN - OPUS4-20151
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Sample spot heterogeneity investigated by MALDI-imaging mass spectrometry
T2 - 18th International Mass Spectrometry Conference
CY - Bremen, Germany
DA - 2009-08-30
PY - 2009
AN - OPUS4-19989
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Cyclic polylactides via ring-expansion polymerization
N2 - We will report on a new kind of ring-expansion polymerization (REP) of cyclic esters based of three classes of catalysts.
In contrast to REP described previously these new polymerizations are characterized by a self-extrusion of the catalysts resulting in cyclic homopolyesters as the only reaction product. These REP of L-lactide were performed in bulk at temperatures between 100 and 180°C without racemization. A simplified scheme of a REP catalyzed by BuCa or SnBi is presented below. With meso-lactide temperatures down to 60°C were realized. Depending on catalyst, time and temperature with equal quantities of even and odd-numbered cycles a strong predominance of either even or odd-numbered cycles was found.
T2 - 255th ACS National Meeting
CY - New Orleans, LA, USA
DA - 18.03.2018
KW - MALDI-TOF MS
KW - Poly(lactide)
KW - Polymerisation
KW - Catalysts
PY - 2018
AN - OPUS4-44833
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF MS von ultra-hochmolekularen Polystyrolen mittels DCTB und Cäsium-Salzen
T2 - 19. Kolloquium MALDI und Synthetische Polymere
CY - Berlin
DA - 2015-05-12
PY - 2015
AN - OPUS4-33055
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF Imaging Mass Spectrometry - an universal detector for copolymer chromatography
T2 - ASMS-Conference on Mass Spectrometry
CY - Denver, CO, USA
DA - 2011-06-04
PY - 2011
AN - OPUS4-23732
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Charakterisierung der molekularen und chemischen Heterogenität von Polyoxymethylen (POM)
T2 - BASF
CY - Ludwigshafen am Rhein, Germany
DA - 2005-06-17
PY - 2005
AN - OPUS4-11143
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
A1 - Krüger, Ralph-Peter
A1 - Just, Ulrich
T1 - Principle of Two-Dimensional Characterization of Copolymers
N2 - Two-dimensional polymer characterization is used for a simultaneous analysis of molar masses and chemical heterogeneities (e.g., end groups, copolymer composition, etc.). This principle is based on coupling of two different chromatographic modes. Liquid adsorption chromatography at critical conditions (LACCC) is applied for a separation according to the chemical heterogeneity, whereas in the second-dimension fractions are analyzed with regard to their molar mass distribution by means of size exclusion chromatography (SEC). Because appropriate standards for a calibration of the SEC are seldom available, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) was used to substitute the SEC. The LACCC-MALDI MS coupling enables acquiring additional structural information on copolymer composition, which can considerably enhance the performance of this coupled method.
KW - MALDI-TOF MS
KW - Chromatographie
KW - Kopplung
PY - 2007
DO - https://doi.org/10.1021/ac062145f
SN - 0003-2700
SN - 1520-6882
VL - 79
IS - 13
SP - 4814
EP - 4819
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-17722
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Friedrich, Jörg Florian
A1 - Schulz, Eckhard
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
T1 - Improvement in Mechanical Strength of Fibre Polymer Composites by Fibre Pretreatment in Low-Pressure Plasmas
T2 - Vortragsbände des 8. Internationalen Techtextil-Symposiums 1997
CY - Frankfurt am Main, Deutschland
DA - 1997-05-12
PY - 1997
SP - 1(?)
EP - 16(?)
PB - Messe Frankfurt
CY - Frankfurt am Main
AN - OPUS4-7286
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Sample spot heterogeneity investigated by MALDI-imaging mass spectrometry
T2 - 57th ASMS Conference On Mass Spectrometry and Allied Topics
CY - Philadelphia, PA, USA
DA - 2009-05-31
PY - 2009
AN - OPUS4-19191
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Falkenhagen, Jana
A1 - Krüger, Ralph-Peter
A1 - Schulz, Günter
A1 - Weidner, Steffen
T1 - Polymer Characterization by LC / MALDI-MS Coupling
T2 - Vortragstagung "Funktionspolymere für Systemlösungen"
CY - Darmstadt, Germany
DA - 2002-03-18
PY - 2002
AN - OPUS4-1805
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - ^Mass spectrometry of synthetic polymers applications and limitations of the MALDI-TOF technique
T2 - APST 2 (Advances in Polymer Science and Technology)
CY - Linz, Austria
DA - 2011-09-28
PY - 2011
AN - OPUS4-25271
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Wolff, D.
A1 - Springer, J.
T1 - Phase Behaviour of Copolymers Containing Cholesterol and 4,4' Methoxybiphenyl as Mesogenic Group
PY - 1996
SN - 0267-8292
SN - 1366-5855
VL - 20
IS - 5
SP - 587
EP - 593
PB - Taylor & Francis
CY - London
AN - OPUS4-11094
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Fandrich, Nick
A1 - Falkenhagen, Jana
A1 - Weidner, Steffen
A1 - Pfeifer, Dietmar
A1 - Staal, B.
A1 - Thünemann, Andreas
A1 - Laschewsky, A.
T1 - Characterization of new amphiphilic block copolymers of N-vinyl pyrrolidone and vinyl acetate, 1 - analysis of copolymer composition, end groups, molar masses and molar mass distributions
N2 - New amphiphilic block copolymers consisting of N-vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4-dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. 13C NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, 13C NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non-ideal RAFT mechanism.
KW - Amphiphiles
KW - Block copolymers
KW - Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS)
KW - N-vinyl pyrrolidone
KW - Reversible addition/fragmentation chain transfer (RAFT)
PY - 2010
DO - https://doi.org/10.1002/macp.200900466
SN - 1022-1352
SN - 1521-3935
VL - 211
IS - 8
SP - 869
EP - 878
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-21905
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Krüger, Rita
A1 - Kelm, Jürgen
A1 - Kretzschmar, Hans-Jürgen
A1 - Schulze, Dietmar
A1 - Trubiroha, Peter
A1 - Weidner, Steffen
T1 - Polymergebundene Ozonschutzmittel - Die bessere Alternative
N2 - Es wurde die Wirksamkeit von zwei neuen Klassen polymergebundener Alterungsschutzmittel (PAS) auf der Basis von N-substituierten p-Phenylendiamin PPD`s (Thioether und Sulfoxide) im Vergleich zu N-Phenyl-N'- (1,3-dimethylbutyl)-p-phenylendiamin (6PPD) in verschiedenen Alterungsbeanspruchungen an unterschiedlichen Elastomeren getestet, der chemische Einbau als Ursache für das günstigere Verhalten hinsichtlich der Minimierung der Rissbildung bei Ozoneinwirkung, Verfärbung und Kontaktverfärbung sowie der Bildung von primären aromatischen Aminen (PAA) analytisch nachgewiesen.
PY - 2004
UR - http://www.plastverarbeiter.de/ai/resources/0987633eb37.pdf
SN - 0948-3276
SN - 0022-9520
VL - 57
IS - 4
SP - 179
EP - 183
PB - Hüthig
CY - Heidelberg
AN - OPUS4-4712
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Knappe, Patrick
A1 - Bienert, Ralf
A1 - Weidner, Steffen
A1 - Thünemann, Andreas
T1 - Characterization of poly/N-vinyl-2-pyrrolidone)s with broad size distributions
N2 - We report on the characterization of the solution structure of poly(N-vinyl-2-pyrrolidone)s (PVP) by small-angle X-ray scattering (SAXS) and by online coupling of asymmetrical flow field-flow fractionation (A4F), SAXS and dynamic light scattering (DLS). The commercial products PVP K30 and PVP K90 with nominal molar masses of 40 × 103 and 360 × 103 g mol-1, respectively, were investigated separately and as binary mixture. Detailed information for all polymer fractions is available on the polymer contour lengths and the diffusion coefficients. Key areas of applications for the A4F-SAXS-DLS coupling are seen in comparison to static light scattering for polymers with radii of gyration smaller than 10 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution.
KW - Small-angle X-ray scattering
KW - SAXS
KW - Field-flow fractionation
PY - 2010
DO - https://doi.org/10.1016/j.polymer.2010.02.039
SN - 0032-3861
SN - 1873-2291
VL - 51
IS - 8
SP - 1723
EP - 1727
PB - Springer
CY - Berlin
AN - OPUS4-21222
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Yu, Z.
A1 - Weidner, Steffen
A1 - Risse, T.
A1 - Hecht, S.
T1 - The role of statistics and microenvironment for the photoresponse in multi-switch architectures: The case of photoswitchable oligoazobenzene foldamers
N2 - Systems containing multiple photochromic units possibly display a synergistic interplay of individual switching events and hence potentially give rise to unprecedented photoresponsive behavior. Among such systems photoswitchable foldamers are attractive as the photoisomerization events are coupled to the helixcoil conformational transition. To gain comprehensive insight into the role of the number of switching units (statistics) as well as their specific location and relative orientation in the helix backbone, several series of foldamers have been synthesized and characterized. In these series of foldamers, the local environment of the photoswitchable units was precisely tuned as π,π-stacking interactions were enforced to occur between specific pairs, i.e. azobenzene–azobenzene, azobenzene–tolane, or phenylene–phenylene units. These particular arrangements are reflected not only in the stability of the helical conformation, but also affect the photoresponsive behavior, i.e. the rate of photoisomerization and extent of denaturation. Furthermore, determining the intramolecular spin–spin distance in a series of TEMPO-labeled foldamers with variable chain lengths and different spatial locations of the spin-labels deduced an independent verification of the photoinduced helix–coil transition by ESR spectroscopy. Quantitative analysis of the corresponding ESR spectra shows an excellent correlation of the extent of intramolecular spin–spin coupling and the intensity of the Cotton effect in CD spectroscopy. From all of these results an unusual relationship between the rate of photoisomerization and the extent of photoinduced denaturation could be unraveled, as they are not going hand-in-hand but compete with each other, i.e. the easier the individual switching event is, the harder it becomes to achieve a high degree of unfolding. This insight into the effect of microenvironment on the ease of individual switching events and the role of statistics on the resulting degree of the overall conformational transition is of general interest for the design of multi-switch architectures with improved photoresponse.
KW - Polymers
KW - Photoswitchable
KW - Oligoazobenzene
KW - Foldamers
PY - 2013
DO - https://doi.org/10.1039/c3sc51664d
SN - 2041-6520
SN - 2041-6539
VL - 4
IS - 11
SP - 4156
EP - 4167
PB - RSC
CY - Cambridge
AN - OPUS4-29814
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H. R.
T1 - Alcohol-initiated and Tin(II) 2-ethylhexanoate-catalyzed polymerization of L-lactide in bulk – About separate crystallization of cyclic and linear Poly (L-lactide)s
N2 - Alcohol-initiated ROPs of L-Lactide were performed at 140 ◦C in bulk with variation of the initiator/catalyst ratio and time. Lower ratios favor the formation of cycles which upon annealing display a change of the MALDI mass peak distribution towards a new maximum with a “saw-tooth pattern” of the mass peaks representing the cycles.
Such a pattern was not observed for the mass peak of the linear chains. The coexistence of these patterns indicate that linear and cyclic poly (L-lactide)s (PLA) crystallize in separate crystals, and that the crystallites of the cycles are made up by extended rings. High Tm and ΔHm values confirm that these extended-ring crystallites represent a thermodynamically optimized form of PLA. Experiments with preformed cyclic and linear PLAs support this interpretation.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
KW - Polymerization
PY - 2023
DO - https://doi.org/10.1016/j.polymer.2023.126355
VL - 285
IS - 126355
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-58355
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - About formation of cycles in Sn(II) octanoate-catalyzed polymerizations of lactides
N2 - At first, formation of cycles in commercial poly(Llactide)s is discussed and compared with benzyl alcoholinitiated polymerizations performed in this work. This comparison was extended to polymerizations initiated with 4-cyanophenol and pentafluorothiophenol which yielded cyclic polylactides via end-biting. The initiator/catalyst ratio and the acidity of the initiator were found to be decisive for the extent of cyclization. Further polymerizations of L-lactide were performed with various diphenols as initiators/co-catalysts. With most diphenols, cyclic polylactides were the main reaction products. Yet, only catechols yielded even-numbered cycles as main reaction products, a result which proves that their combination with SnOct2 catalyzed a ring-expansion polymerization (REP). The influence of temperature, time, co-catalyst, and catalyst concentrations was studied. Four different transesterification reactions yielding cycles were identified. For the cyclic poly(L-lactide)s weight average molecular weights (Mw’s) up to 120,000 were obtained, but 1H NMR end group analyses indicated that the extent of cyclization was slightly below 100%.
The influence of various parameters like structure of Initiator and catalyst and temperature on the formation of cyclic poly(Llactide)s has been investigated. Depending on the chosen conditions, the course of the polymerization can be varied from a process yielding exclusively linear polylactides to mainly cyclic polylactides. Three different reaction pathways for cyclization reactions have been identified.
KW - Cyclization
KW - MALDI-TOF MS
KW - Polyester
KW - Ring-opening polymerization
KW - Transesterification
PY - 2018
DO - https://doi.org/10.1002/pola.29077
SN - 0887-624X
VL - 56
IS - 17
SP - 1915
EP - 1925
PB - Wiley Periodicals Inc.
AN - OPUS4-46052
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Barner‐Kowollik, C.
A1 - Falkenhagen, Jana
A1 - Gründling, T.
A1 - Weidner, Steffen
ED - Barner-Kowollik, C.
ED - Gründling, T.
ED - Falkenhagen, Jana
ED - Weidner, Steffen
T1 - Introduction
N2 - The book opens with an overview of the available mass analyzers. Special consideration is given by the authors Steven Blanksby and Gene Hart-Smith to their uses in polymer chemistry. Various ionization techniques applicable in polymer mass spectrometry are then explored in-depth by Anthony Gies. Chrys Wesdemiotis subsequently takes a close look at tandem mass spectrometry, a highly important tool for the elucidation of polymer structure and one of the major contemporary fields of development in the mass spectrometry sector. Sarah Trimpin and colleagues follow with their contribution, describing gas-phase ion-separation procedures as applied to synthetic polymers. The ionization process of polymers via the MALDI approach requires a careful design of the sample preparation procedures. Scott Hanton and Kevin Owens therefore provide a close look at how polymer samples are best prepared. Synthetic polymers are not only important materials in their own right, but are also frequently employed to (covalently) modify variable surfaces. Surface analysis is notoriously challenging and a range of techniques have to be employed to map the chemical characteristics of surface-bound macromolecules. Christine Mahoney and Steffen Weidner provide a detailed description of the part which surface-sensitive mass spectrometric techniques play in elucidating a polymer surface’s structure.
Soft ionization mass spectrometry techniques can be especially powerful when combined with chromatographic techniques such as size exclusion chromatography (SEC), liquid adsorption chromatography at critical conditions (LACCCs) or both. Jana Falkenhagen and Steffen Weidner explore the wide variety of so-called hyphenated techniques and impressively demonstrate the information depth that can be attained by employing such technologies. While arguably the majority of molecular weight determination is carried out via SEC often equipped with refractive index as well as light scattering detectors, Till Gruendling, William Wallace, and colleagues demonstrate how MALDI-MS as well as SEC coupled to ESI-MS can be employed to deduce absolute molecular weight distributions. The chapter also provides an overview of contemporary automated data processing techniques for mass spectrometric data. Most polymers generated are arguably copolymers and it thus is mandatory to dedicate an entire chapter to the analysis of copolymers via mass spectrometry — Ulrich Schubert and Anna Crecelius provide an in-depth analysis.
The field of living/controlled radical polymerization provides fascinating high precision avenues for the construction of complex macromolecular architectures and enables the generation of polymers with a high degree of end-group fidelity, which are often employed in cross-discipline applications (e.g., in biosynthetic conjugates). Soft ionization mass spectrometry plays an integral part in unravelling the mechanism of living/controlled radical polymerization processes as well as in the characterization of macromolecular building blocks: Christopher Barner-Kowollik and colleagues take a close look at the current state-of-the-art. Similarly, polymers generated via conventional radical polymerization can be readily investigated via mass spectrometry. Here, especially the investigation of the initiation process and of the generated end-group type is of high importance — Michael Buback, Greg Russell, and colleagues report. Finally, Grazyna Adamus and Marek Kowalczuk survey the field of mass spectrometry applied to polymers prepared via nonradical methods such as coordination polymerization, polycondensation, and polyaddition. The question of polymer stability and a detailed understanding of polymer degradation processes on a molecular level are of paramount importance for an evaluation of the performance of a polymer in chemical applications or as a material. Sabrina Carroccio and colleagues survey the field of soft ionization mass spectrometry applied to the molecular study of degradation processes at the book’s conclusion.
KW - Mass spectrometry
KW - Polymers
PY - 2012
SN - 978-3-527-32924-3
SN - 978-3-527-64182-6
DO - https://doi.org/10.1002/9783527641826.ch
SP - 1
EP - 4
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-65732
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Robinson, J.W.
A1 - Secker, C.
A1 - Weidner, Steffen
A1 - Schlaad, H.
T1 - Thermoresponsive poly(N-C3 glycine)s
N2 - Ring-opening polymerization of N-substituted glycine N-carboxyanhydrides (NCAs) was applied to prepare a series of well-defined poly(N-C3 glycine)s (C3 = n-propyl, allyl, propargyl, and isopropyl), polypeptoids, with molecular weights in the range of 1.8–6.6 kg mol–1. Poly(N-isopropyl glycine), a previously unreported polypeptoid, could be obtained by bulk polymerization of the corresponding NCA in the melt. The samples were characterized by spectroscopy (NMR and FT-IR), size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI–ToF MS). The polymers could be dispersed in water up to 20–40 g L–1; the poly(N-propargyl glycine) was not soluble in water. Turbidity measurements of the three water-soluble polypeptoids illustrated cloud point temperatures dependent on structural and electronic properties of the side chain. The cloud point temperatures were found to increase in the order C3 = n-propyl (15–25 °C) < allyl (27–54 °C) < isopropyl (47–58 °C). Long-term annealing of the aqueous solution of poly(N-{n-propyl} glycine) and poly(N-allyl glycine) above the cloud point temperature resulted in the formation of crystalline microparticles with melting points of 188–198 and 157–165 °C (differential scanning calorimetry, DSC), respectively, and rose bud type morphology (scanning electron microscopy, SEM).
PY - 2013
DO - https://doi.org/10.1021/ma302412v
SN - 0024-9297
SN - 1520-5835
VL - 46
IS - 3
SP - 580
EP - 587
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-27696
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.R.
A1 - Weidner, Steffen
T1 - High Tg copolyesters of lactide, isosorbide and isophthalic acid
N2 - Using SnCl2, ZnCl2, Zn-lactate or Zr-acetylacetonate as catalysts ʟ-lactide was oligomerized in bulk with isosorbide as initiator. The ratio isosorbide/lactide was varied from 8/2 to 2/8. The resulting oligomers were in situ polycondensed with isophthaloyl chloride in various aromatic solvents. In chlorobenzene homogeneous reaction mixtures were obtained, whereas molten copolyesters precipitated from toluene and xylene. The obtained average molecular weights indicated high polydispersities. According to MALDI-TOF MS the low molar mass reaction products (<4 kDa) almost exclusively consisted of cyclics with a composition depending on the feed ratio. The glass-transition temperatures (Tg) varied between the values of poly(ʟ-lactide (64 °C) and poly(isosorbide isophthalate) (180 °C). Four polyesters prepared from 5-tert-butyl isophthalic acid displayed higher Tg values. Differential thermoanalysis evidenced that the thermostability decreases with higher fractions of lactide, but processing from the melt seems to be feasible up to temperatures of 260 °C without risking degradation.
KW - Lactide
KW - Isosorbide
KW - Ring-opening polymerization
KW - Polycondensation
KW - Cyclization
PY - 2013
DO - https://doi.org/10.1016/j.eurpolymj.2013.05.007
SN - 0014-3057
SN - 1873-1945
VL - 49
IS - 8
SP - 2293
EP - 2302
PB - Elsevier
CY - Oxford
AN - OPUS4-29014
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Trimpin, S.
A1 - Inutan, E.
A1 - Karki, S.
A1 - Elia, E.
A1 - Zhang, W.
A1 - Weidner, Steffen
A1 - Marshall, D.
A1 - Hoang, K.
A1 - Lee, C.
A1 - Davis, E.
A1 - Smith, V.
A1 - Meher, A.
A1 - Cornejo, M.
A1 - Auner, G.
A1 - McEwen, C.
T1 - Fundamental studies of new ionization technologies and insights from IMS-MS
N2 - Exceptional ion mobility spectrometry mass spectrometry (IMS-MS) developments by von Helden, Jarrold, and Clemmer provided technology that gives a view of chemical/biological compositions previously not achievable. The ionization method of choice used with IMS-MS has been electrospray ionization (ESI). In this Special issue contribution, we focus on fundamentals of heretofore unprecedented means for transferring volatile and nonvolatile compounds into gas-phase ions singly and multiply charged. These newer ionization processes frequently lead to different selectivity relative to ESI and, together with IMS-MS, may provide a more comprehensive view of chemical compositions directly from their original Environment such as surfaces, e.g., tissue. Similarities of results using solvent- and matrix-assisted ionization are highlighted, as are differences between ESI and the inlet ionization methods, especially with mixtures such as bacterial extracts. Selectivity using different matrices is discussed, as are results which add to our fundamental knowledge of inlet ionization as well as pose additional avenues for inquiry. IMS-MS provides an opportunity for comparison studies relative to ESI and will prove valuable using the new ionization technologies for direct analyses. Our hypothesis is that some ESI-IMS-MS applications will be replaced by the new ionization processes and by understanding mechanistic aspects to aid enhanced source and method developments this will be hastened.
KW - Inlet ionization
KW - Vacuum ionization
KW - Matrices
KW - Fundamentals
KW - Ion mobility
PY - 2019
DO - https://doi.org/10.1007/s13361-019-02194-7
SN - 1044-0305
SN - 1879-1123
VL - 30
IS - 6
SP - 1133
EP - 1147
PB - Springer
AN - OPUS4-48011
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sötebier, Carina
A1 - Weidner, Steffen
A1 - Jakubowski, Norbert
A1 - Panne, Ulrich
A1 - Bettmer, J.
T1 - Separation and quantification of silver nanoparticles and silver ions using reversed phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry in combination with isotope dilution analysis
N2 - A reversed phase high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICP-MS) approach in combination with isotope dilution analysis (IDA) for the separation and parallel quantification of nanostructured and ionic silver (Ag) is presented. The main focus of this work was the determination of the ionic Ag concentration. For a sufficient stabilization of the ions without dissolving the nanoparticles (NPs), the eluent had to be initially optimized. The determined Ag ion concentration was in a good agreement with results obtained using ultrafiltration. Further, the mechanism of the NP separation in the HPLC column was investigated. Typical size exclusion effects were found by comparing results from columns with different pore sizes. Since the recovery rates decreased with increasing Ag NP size and large Ag NPs did not elute from the column, additional interactions of the particles with the stationary phase were assumed. Our results reveal that the presented method is not only applicable to Ag NPs, but also to gold and polystyrene NPs. Finally, IDA-HPLC-ICP-MS experiments in single particle mode were performed to determine the particle cut-off size. The comparison with conventional spICP-MS experiments resulted in a similar diameter and particle size distribution.
KW - ICP-MS
KW - Silver nanoparticles
KW - HPLC
KW - Isotope dilution analysis
KW - Field flow fractionation
KW - Toxicology
PY - 2016
DO - https://doi.org/10.1016/j.chroma.2016.09.028
SN - 0021-9673
VL - 1468
SP - 102
EP - 108
PB - Elsevier B.V.
AN - OPUS4-38642
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.R.
A1 - Weidner, Steffen
A1 - Lahcini, M.
T1 - Multicyclic polyesters of trimesic acid and alkanediols and the theory of network formation
N2 - Trimesoyl chloride is polycondensed with various alpha,omega'-alkanediols in dichloromethane at different concentrations using equifunctional feed ratios. As evidenced by MALDI-TOF (matrix assisted laser desorption/ionization-time of flight) mass spectrometry the soluble reaction products mainly consist of perfect multicyclic oligomers and polymers. The solphase extracted from the gels also consists of perfect multicycles. SEC (size exclusion chromatography) measurements show that both soluble reaction products and extracted solphases also contain a high molar mass fraction of perfect and nonperfect multicycles extending up to masses beyond 10 5 g mol-1. When the polycondensation is stopped after a few minutes perfect multicycles are already detectable in the reaction mixture along with functional (multi)cyclic oligomers. These results prove that at initial monomer concentrations < 0.2 mol L-1 networks and large multicyclic polymers are synthesized from functional cyclic oligomers formed in early stages of the polycondensation and not from hyperbranched polymers. This interpretation is presented as 'egg-first theory' and compared with the 'hen-first theory' of Stockmayer and Flory.
KW - a2 + b3 polycondensation
KW - Cyclization
KW - MALDI
KW - Multicyclic polymers
KW - Networks
PY - 2015
DO - https://doi.org/10.1002/macp.201500245
SN - 1022-1352
SN - 1521-3935
VL - 216
IS - 21
SP - 2095
EP - 2106
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-35282
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Thünemann, Andreas
A1 - Knappe, Patrick
A1 - Bienert, Ralf
A1 - Weidner, Steffen
T1 - Online coupling of field-flow fractionation with SAXS and DLS for polymer analysis
N2 - We report on a hyphenated polymer analysis method consisting of asymmetrical flow field-flow fractionation (A4F) coupled online with small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). A mixture of six poly(styrene sulfonate)s with molar masses in the range of 6.5 × 103 to 1.0 × 106 g mol-1 was used as a model system for polyelectrolytes in aqueous solutions with a broad molar mass distribution. A complete polymer separation and analysis was performed in 60 min. Detailed information for all polymer fractions are available on i) the radii of gyration, which were determined from the SAXS data interpretation in terms of the Debye model (Gaussian chains), and ii) the diffusion coefficients (from DLS). We recommend using the A4F-SAXS-DLS coupling as a possible new reference method for the detailed analysis of complex polymer mixtures. Advantages of the use of SAXS are seen in comparison to static light scattering for polymers with radii of gyration smaller then 15 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution.
PY - 2009
DO - https://doi.org/10.1039/b9ay00107g
SN - 1759-9660
SN - 1759-9679
VL - 1
SP - 177
EP - 182
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-20567
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sötebier, Carina A.
A1 - Weidner, Steffen
A1 - Jakubowski, Norbert
A1 - Panne, Ulrich
A1 - Bettmer, J.
T1 - Separation and quantification of silver nanoparticles and silver ions using reversed phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry in combination with isotope dilution analysis
N2 - A reversed phase high performance liquid chromatography coupled to an inductively coupled Plasma mass spectrometer (HPLC–ICP-MS) approach in combination with isotope dilution analysis (IDA) for the separation and parallel quantification of nanostructured and ionic silver (Ag) is presented. The main Focus of this work was the determination of the ionic Ag concentration. For a sufficient stabilization of the Ions without dissolving the nanoparticles (NPs), the eluent had to be initially optimized. The determined Ag ion concentration was in a good agreement with results obtained using ultrafiltration. Further, the mechanism of the NP separation in the HPLC column was investigated. Typical size exclusion effects were found by comparing results from columns with different pore sizes. Since the recovery rates decreased with increasing Ag NP size and large Ag NPs did not elute from the column, additional interactions of the particles with the stationary phase were assumed. Our results reveal that the presented method is not only applicable to Ag NPs, but also to gold and polystyrene NPs. Finally, IDA-HPLC-ICP-MS experiments in single particle mode were performed to determine the particle cut-off size. The comparison with conventional spICP-MS experiments resulted in a similar diameter and particle size distribution.
KW - ICP-MS
KW - Silver nanoparticles
KW - Speciation
KW - High performance liquid chromatography
KW - Isotope dilution analysis
PY - 2016
DO - https://doi.org/10.1016/j.chroma.2016.09.028
SN - 0021-9673
VL - 1468
SP - 102
EP - 108
AN - OPUS4-37652
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans
A1 - Weidner, Steffen
T1 - High molar mass cyclic poly(L-lactide) via ring-expansion polymerizationwith cyclic dibutyltin bisphenoxides
N2 - Two new catalysts (SnNa and SnBi) were prepared from dibutyltin oxide and 2,2′-dihydroxybiphenyl or2,2′dihydroxy(1,1′-binaphtyl). These catalysts enabled rapid polymerizations of L-lactide at 160 or 180 °C in bulk, whereby almost exclusively cyclic polylactides were formed. These polymerizations were free of racemization and yielded pol(L-lactide)s having weight average molecular weights (Mw's) up to 140 000 g mol−1. The Mw's varied little with the Lac/Cat ratio as expected for a ring expansion polymerization (REP). Polymerizations performed in bulk at 140, 120 and 102 °C yielded cyclic polylactides with lower molecular weights. At 102 °C a strong predominance of even-numbered cycles was found with SnNa as catalyst. SnNa can also catalyze alcohol-initiated ROPs yielding linear poly(L-lactide) free of cyclics.
KW - MALDI-TOF MS
KW - Polylactide
KW - Ring-opening Polymerization
KW - Cyclization
KW - Catalysts
PY - 2018
DO - https://doi.org/10.1016/j.eurpolymj.2018.05.036
SN - 0014-3057
SN - 1873-1945
VL - 105
SP - 158
EP - 166
PB - Elsevier Ltd.
AN - OPUS4-45439
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Billing, Mark
A1 - Gräfe, Christine
A1 - Saal, Adrian
A1 - Biehl, Philip
A1 - Clement, Joachim
A1 - Dutz, silvio
A1 - Weidner, Steffen
A1 - Schacher, Felix
T1 - Zwitterionic Iron Oxide (γ-Fe2O3) Nanoparticles Based on P(2VP-grad-AA) Copolymers
N2 - This study presents the synthesis and characterization of zwitterionic core–shell hybrid nanoparticles consisting of a core of iron oxide multicore nanoparticles (MCNPs, γ-Fe2O3) and a shell of sultonated poly(2-vinylpyridine-grad-acrylic acid) copolymers. The gradient copolymers are prepared by reversible addition fragmentation chain transfer polymerization of 2-vinylpyridine (2VP), followed by the addition of tert-butyl acrylate and subsequent hydrolysis. Grafting of P(2VP-grad-AA) onto MCNP results in P(2VP-grad-AA)@MCNP, followed by quaternization using 1,3-propanesultone-leading to P(2VPS-grad-AA)@MCNP with a zwitterionic shell. The resulting particles are characterized by transmission electron microscopy, dynamic light scattering, and thermogravimetric analysis measurements, showing particle diameters of ≈70–90 nm and an overall content of the copolymer shell of ≈10%. Turbidity measurements indicate increased stability toward secondary aggregation after coating if compared to the pristine MCNP and additional cytotoxicity tests do not reveal any significant influence on cell viability.
KW - Blockcopolymer
KW - Controlled radical polymerization
KW - Hybrid nanoparticles
KW - Iron oxide nanoparticles
KW - Sulfobetaines
PY - 2017
DO - https://doi.org/10.1002/marc.201600637
SN - 1022-1336
SN - 1521-3927
VL - 38
IS - 4
SP - 1600637-1
EP - 1600637-8
PB - Wiley-VCH
AN - OPUS4-39339
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Mechichi, R.
A1 - Chabbah, T.
A1 - Chatti, S.
A1 - Jlalia, I.
A1 - Sanglar, Corinne
A1 - Casablanca, H.
A1 - Vulliet, E.
A1 - Marestin, C.
A1 - Mercier, R.
A1 - Weidner, Steffen
A1 - Errachid, A.
A1 - Hammani, M.
A1 - Jaffrezic-Renault, N.
A1 - Abderrazak, H.
T1 - Semi‑interpenetrating Network‑Coated Silica Gel Based on Green Resources for the Efcient Adsorption of Aromatic Pollutants from Waters
N2 - In the framework of the development of green analytical chemistry, a silica gel (SG) coated with a semi-penetrating network based on the partially biosourced poly(ethersulfone) is studied for a greener extraction process of aromatic organic pollutants. An optimized composition of the semi-penetrating network (80% of the linear polymer (LP): isosorbide-based poly(ethersulfone) and 20% cross-linking agent (XP) type bismaleimide) leads to a total adsorption of the selected aromatic pollutants, whatever their hydrophilicity. Adsorption characteristic, kinetics and isotherms of the SG-semi-INP LP80/XP20 for p-hydroxybenzoic acid and for toluic acid were studied. Langmuir model led to a better ftting of the adsorption isotherms; the adsorption of toluic acid is easier than that of p-hydroxybenzoic acid. 1/n values of benzoic acid was lower for SGsemi-INP LP80/XP20 compared to biochar and to cross-linked methacrylate resin, showing a higher adsorption efciency.
KW - Isosorbide
KW - Semi-interpenetrating networks
KW - Silica gel modification
KW - Aromatic pollutants
KW - Adsorption
PY - 2022
DO - https://doi.org/10.1007/s42250-022-00463
SN - 2522-5758
SP - 1
EP - 18
PB - Springer
AN - OPUS4-55720
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, Hans R.
A1 - Weidner, Steffen
T1 - Ring-expansion polymerization of meso-lactide catalyzed by dibutyltin derivatives
N2 - Meso-Lactide was polymerized in bulk at 60, 80, and 100 °C by means of three different types of catalysts: dibutyltinsulfides (2,2-dibutyl-2-stanna-1,3-dithiolane and 2,20-dibutyl-2-stanna-1,3-dithiane), dibutyltin derivatives of substituted cate-chols (BuCa, CyCa, and BzCa), and dibutyltin derivatives of2,2 dihydroxybiphenyl (SnBi) and 2,2-dihydroxy-1,10-binaphthyl(SnNa. Only the latter two catalysts were active at 60 °C. The architecture of the resulting polylactides depends very much on the structure of the catalyst and on the temperature. At the lowest temperature (60 °C), SnBi and SnNa mainly yielded even-numbered linear chains, but SnNa also yielded even-numbered cycles at 100 °C and short reaction times. In contrast,BuCa, CyCa, and BzCa mainly yielded odd-numbered cycles, although the same catalysts yielded even-numbered linear chains when benzylalcohol was added.
KW - MALDI-TOF MS
KW - Cyclisation
KW - Catalysts
KW - Polyester
KW - Polymerization
PY - 2018
DO - https://doi.org/10.1002/pola.28948
SN - 1099-0518
SN - 0022-3832
VL - 56
IS - 7
SP - 749
EP - 759
PB - Wiley Periodicals Inc.
AN - OPUS4-44278
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H.
T1 - Transesterification in alcohol-initiated ROPs of l- and meso-lactide catalyzed by Sn(II) and Sn(IV) compounds at low temperatures
N2 - The purpose of this study is to shed more light on the transesterification processes in alcohol-initiated and tin(II) 2-ethylhexanoate (SnOct2)-catalyzed polymerizations of lactides at low or moderate temperatures. Ethanol-initiated polymerizations are conducted in concentrated solutions at 80 °C and a strong dependence of even/odd equilibration on the alcohol/Sn ratio. Around or above 120 °C cyclization of poly(l-lactide) via “backbiting” occurs as a third mechanism. However, poly(m-lactide) shows a higher cyclization tendency and yields cyclics even at 100 °C. Combinations of ethanol and certain cyclic dibutyltin(IV) catalysts also yield cyclic oligomers of l-lactide at 80 °C. Reaction conditions allowing for a total suppression of all transesterification reactions are not found, but even-numbered poly(m-lactide)s with a purity >95% are obtained at 70 or 60 °C.
KW - Cyclization
KW - MALDI-TOF MS
KW - Polyester
KW - Polylactide
KW - Transesterification
PY - 2018
DO - https://doi.org/10.1002/macp.201800445
SN - 1022-1352
SN - 1521-3935
VL - 219
IS - 24
SP - 1800445, 1
EP - 10
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-46705
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Cyclic poly(L-lactide)s via simultaneous ROP and polycondensation (ROPPOC) catalyzed by dibutyltin phenoxides
N2 - Starting from dibutyltin oxide, four catalysts were synthesized, namely the dibutyltin bisphenoxides of Phenol (SnPh), 4-chlorophenol (SnCP), 4-hydroxybenzonitrile (SnCN) and pentafluorophenol (SnOPF). With the first three catalysts polymerizations of L-lactide at 160 °C in bulk yielded large fraction of linear chains having phenylester end groups at short reaction times. At longer times the fraction of cycles considerably increased at the expense of the linear chains, when SnCN was used as catalyst. With SnOPF only cyclic polylactides were obtained at low Lac/Cat ratios (< 400) with weight average molecular weights (Mw) up to 90 000 Da, whereas for high Lac/Cat ratios mixtures of cyclic and linear chains were found. Polymerizations in solution enabled variation of the molecular weight. Polymerizations of meso-lactide at temperatures down to 60 °C mainly yielded even-numbered linear chains supporting the postulated ROPPOC mechanism.
KW - Cyclization
KW - MALDI-TOF MS
KW - Polycondensation
KW - Ring-opening Polymerization
KW - Polylactide
PY - 2018
DO - https://doi.org/10.1016/j.eurpolymj.2018.10.005
SN - 0014-3057
IS - 109
SP - 360
EP - 366
PB - Elsevier
AN - OPUS4-46263
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-MS zur Aufklärung des Mechanismus der homogen katalysierten Polymerisation flüssigkristalliner Seitengruppenmethacrylate
T2 - III. BAM-Kolloquium zu "Anwendung von MALDI-MS zur Charakterisierung von synthetischen Polymeren"
CY - Berlin, Germany
DA - 1999-05-17
PY - 1999
AN - OPUS4-11301
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
T1 - Plasmaoxidative Degradation of Polymers Studied by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry
PY - 1996
SN - 0951-4198
SN - 1097-0231
VL - 10
SP - 727
EP - 732
PB - Wiley
CY - Chichester
AN - OPUS4-7004
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Falkenhagen, Jana
A1 - Krüger, Ralph-Peter
A1 - Schulz, Günter
A1 - Weidner, Steffen
T1 - Polymer characterization by LC / MALDI-MS coupling
T2 - Bayreuther Polymer Symposium 2001
CY - Bayreuth, Germany
DA - 2001-09-16
PY - 2001
CY - Bayreuth
AN - OPUS4-2256
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Erste Untersuchungen zur Infrarot-MALDI-MS von Polymeren
T2 - II. BAM-Kolloquium zu "Anwendung von MALDI-MS zur Charakterisierung von synthetischen Polymeren"
CY - Berlin, Germany
DA - 1998-05-04
PY - 1998
AN - OPUS4-11281
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Scheliga, F.
ED - Shaplov, A.
T1 - Cyclization and dispersity of polyesters
N2 - Two classes of polyesters were prepared by irreversible polycondensations.
The dependence of the dispersities on the experimental parameters such as synthetic method, chemical structure, molecular weight and initial monomer concentration was determined. At first it was demonstrated that it is essential for a correct calculation of Mn and Mw to include all oligomers down to the dimers in the evaluation of SEC curves. Furthermore, it was demonstrated for poly(e-caprolactone)s and polylactides that reversible polycondensations and ring-opening polymerizations with equilibration yield identical products.
Finally, the dependence of the dispersity on various experimental Parameters was determined for equilibrated poly(e-caprolactone)s and polylactides.
KW - Irreversible polycondensation
KW - Polycaprolactone
KW - Polylactide
KW - Dispersity
KW - MALDI-TOF MS
PY - 2017
DO - https://doi.org/10.1002/masy.201600169
SN - 1022-1360
SN - 1521-3900
VL - 375
IS - 1
SP - Article 1600169, 1
EP - 6
PB - Wiley-VCH
AN - OPUS4-42407
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Dispersities of Polyesters of Various Diphenols Prepared by Irreversible Polycondensations
N2 - Polyesters of bisphenol-A, bisphenol-P, catechol, and sebacic acid are prepared and different synthetic methods are compared. The diphenols are condensed with sebacoyl chloride either in dichloromethane/pyridine or in refl uxing chlorobenzene without HCl-acceptor. Further- more, bisphenol-A acetate is polycondensed with sebacic acid in bulk. All experiments are worked up so that fractionation is avoided. The extent of cyclization is estimated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) and the molar mass distribution by size exclusion chromatography (SEC). Polycondensations in solution yield larger fractions of cyclics and higher dispersities (up to 11). Polycondensations in bulk give lower fractions of cycles and dispersities from 4.6 to 6.3 for high molar mass polyesters or 2.8 to 3.5 for low molar mass products. Characteristic curves describing the dependence of the dispersity on the initial monomer concentration are elaborated.
KW - cyclization
KW - dispersity
KW - mass spectra
KW - polycondensation
KW - polyesters
PY - 2016
DO - https://doi.org/10.1002/macp.201600004
IS - 217
SP - 1361
EP - 1369
PB - Wiley-VCH Verlag
CY - Weinheim
AN - OPUS4-37120
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Friedrich, Jörg Florian
A1 - Unger, Wolfgang
A1 - Lippitz, Andreas
A1 - Koprinarov, Ivaylo
A1 - Weidner, Steffen
A1 - Kühn, Gerhard
ED - Schindel-Bidinelli, E.
T1 - Umweltfreundliches Metallisieren von Kunststoffen durch Plasmavorbehandlung in einem geschlossenen Reaktor
T2 - Swissbonding 97 ; 11. Internationales Symposium Klebtechnik und Umwelt ; 11th International Symposium Bonding and Sealing Technology
CY - Rapperswil, Schweiz
DA - 1997-05-26
PY - 1997
SP - 1(?)
EP - 3(?)
PB - SWIBOTECH
CY - Rorbas
AN - OPUS4-6994
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Falkenhagen, Jana
T1 - Imaging mass spectrometry for examining localization of polymeric composition in matrix-assisted laser desorption/ionization samples
N2 - The localization of polymeric composition in samples prepared for matrix-assisted laser desorption/ionization (MALDI) analysis has been investigated by imaging mass spectrometry. Various matrices and solvents were used for sample spot preparation of a polybutyleneglycol (PBG 1000). It was shown that in visibly homogeneous spots, prepared using the dried droplet method, separation between matrix and polymer takes place. Moreover, using -cyano-4-hydroxycinnamic acid (CCA) as matrix and methanol as solvent molecular mass separation of the polymer homologues in the spots was detectable. In contrast to manually spotted samples, dry spray deposition results in homogeneous layers showing no separation effects.
KW - Imaging
KW - MALDI TOF Massenspektrometrie
KW - Polymere
PY - 2009
DO - https://doi.org/10.1002/rcm.3919
SN - 0951-4198
SN - 1097-0231
VL - 23
IS - 5
SP - 653
EP - 660
PB - Wiley
CY - Chichester
AN - OPUS4-19622
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Untersuchung von plasmamodifizierten Polymeren mit speziellen Analysenmethoden
T2 - Abteilungsseminar, BAM, Abt. VI
CY - Berlin, Germany
DA - 1996-05-02
PY - 1996
AN - OPUS4-6411
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Mühlhan, C.
A1 - Weidner, Steffen
A1 - Friedrich, Jörg Florian
A1 - Nowack, H.
T1 - Improvement of bonding properties of polypropylene by low-pressure plasma treatment
PY - 1999
SN - 0257-8972
VL - 116-119
SP - 783
EP - 787
PB - Elsevier Science
CY - Lausanne
AN - OPUS4-6982
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF-MS for the determination of polymerization mechanisms of biodegradable polymers
N2 - Eine neue Art einer Ring-Expansion Polymerization (REP) von zyklischen Polylaktiden mittels neuer Katalysatoren wird präsentiert.
MALDI-TOF Massenspektrometrie und andere analytische Techniken wurden zur Aufklärung des Mechanismus eingesetzt. Dabei zeigte sich, dass im Gegensatz zu anderen REP, ausschließlich zyklische Polymere gebildet wurden. Diese stellen neue Kandidatenmaterialien für zukünftige neue CRM dar.
T2 - 22. MALDI-Kolloquium
CY - Berlin, Germany
DA - 15.05.2018
KW - MALDI-TOF MS
KW - Polylaktid
KW - Zyklen
PY - 2018
AN - OPUS4-44835
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gabriel, Stefan
A1 - Schwarzinger, C.
A1 - Schwarzinger, B.
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Matrix segregation as the major cause for sample inhomogeneity in MALDI dried droplet spots
N2 - The segregation in dried droplet MALDI sample spots was analyzed with regard to the matrix-to-sample ratio using optical microscopy, MALDI imaging mass spectrometry (MALDI MSI) and IR imaging spectroscopy. In this context, different polymer/matrix/solvent systems usually applied in the analysis of synthetic polymers were investigated. The use of typical matrix concentrations (10 mg mL-1) in almost every case resulted in ring patterns, whereas higher concentrated matrix solutions always led to homogeneous sample spot layers. The data revealed that segregation is predominantly caused by matrix transport in the drying droplet, whereas polymer segregation seems to be only secondary.
KW - MALDI
KW - Imaging MS
KW - Matrix segregation
KW - Dried droplet
KW - Sample preparation
KW - Polymers
PY - 2014
DO - https://doi.org/10.1007/s13361-014-0913-0
SN - 1044-0305
VL - 25
IS - 8
SP - 1356
EP - 1363
PB - American Society for Mass Spectrometry
CY - New York, NY
AN - OPUS4-32582
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Improved analysis of ultra-high mass polymers in MALDI-TOF mass spectrometry
T2 - ASMS 2015
CY - St. Louis (USA)
DA - 2015-05-30
PY - 2015
AN - OPUS4-33446
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - About the crystallization of cyclic and linear poly(L-lactide)s in alcohol-initiated and Sn(II)2-ethylhexanoate- catalyzed ROPs of L-lactide conducted in solution
N2 - 1-Hydroxymethylnaphtalene (HMN) or 11-bromoundecanol (BUND) were used as initiators and Sn(II) 2-ethylhexanoate (SnOct2) as catalyst for ROPs of L-Lactide (LA) at 115 °C in bulk or in 4 M and 2M solutions in toluene. The LA/In ratio, the LA/Cat ratio and the time were varied. The matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectra exclusively displayed peaks of linear chains, when the ROPs were conducted in bulk. But in contrast to reports in the literature, mixtures of linear and cyclic poly(L-lactide) (PLA), were obtained, when the ROPs were performed in solution. The intensity distribution of the mass peaks of cyclic PLAs displayed a “saw-tooth pattern” after annealing in contrast to the mass peak distribution of the liner chains. This new phenomenon indicated that cyclic PLAs and linear PLAs crystallized in separate crystals from the same reaction mixture. This conclusion was confirmed by fractionated crystallization from 2 M solution, which confirmed that the cyclic PLAs nucleate and crystallize faster than the linear chains.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring opening polymerization
KW - Crystallization
PY - 2023
DO - https://doi.org/10.1016/j.polymer.2023.125946
SN - 0032-3861
VL - 276
SP - 1
EP - 11
PB - Elsevier Ltd.
AN - OPUS4-57308
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Cappella, Brunero
A1 - Sturm, Heinz
A1 - Weidner, Steffen
T1 - Breaking polymer chains by dynamic plowing lithography
N2 - The adhesion of poly(methyl methacrylate) (PMMA) and polystyrene (PS) films, whose surface has been previously structured by dynamic plowing lithography (DPL), has been measured by means of forcedisplacement curves. The different adhesion of modified and unmodified PS leads to the assumption that polymer chains are broken during DPL. After measuring the energy dissipated by the tip during DPL, in order to check that the transferred energy is sufficient to break covalent bonds, the polymer chain scission caused by the lithographic process has been definitely confirmed by size exclusion chromatography measurements of the lithographed films.
KW - AFM
KW - Nanolithography
KW - Chain scission
PY - 2002
DO - https://doi.org/10.1016/S0032-3861(02)00285-9
SN - 0032-3861
SN - 1873-2291
VL - 43
IS - 16
SP - 4461
EP - 4466
PB - Springer
CY - Berlin
AN - OPUS4-1608
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Alcohol-Initiated and SnOct2-Catalyzed Ring-Opening Polymerization (ROP) of L-Lactide in Solution: A Re-investigation
N2 - Alcohol-initiated ring-opening polymerizations (ROP) of L-lactide (LA) were studied in solution at 70 °C, whereupon the nature of the alcohol, the LA/initiator ratio, the LA/SnOct2 ratio and the time were varied. In contrast to literature, neat SnOct2 is catalytically active in THF and several aromatic but donor solvents, such as 1,3-dioxolane, dimethylformamide (DMF) or N-methyl pyrrolidone (NMP), strongly reduce the activity of SnOct2. In agreement with literature, no cycles were formed by neat SnOct2 at 70 °C in toluene, whereas almost complete cyclization occurs at 115 °C. This finding is attributed to strongly reduced mobility of the initially formed linear chains having one Sn-O-CH and one anhydride end group. Due to better solvation and enhanced mobility cyclization occurs in THF at 70 °C.
KW - Polylactide
KW - Ring-opening polymerization
KW - MALDI-TOF MS
KW - Transesterification
PY - 2023
DO - https://doi.org/10.1016/j.eurpolymj.2023.111822
SN - 0014-3057
SP - 1
EP - 18
PB - Elsevier
CY - New York, NY [u.a.]
AN - OPUS4-56818
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - GEN
A1 - Weidner, Steffen
T1 - Rezension: Kompakte Zusammenfassung - MALDI-TOF Mass Spectrometry of Synthetic Polymers. Von H. Pasch, W. Schrepp. Springer, Heidelberg 2003, 298 Seiten. geb., 79,95 Euro. ISBN 3-540-44259-6
PY - 2003
DO - https://doi.org/10.1002/nadc.20030511123
SN - 1439-9598
SN - 1521-3854
VL - 51
IS - 11
SP - 1173
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-4678
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gross, J.H.
A1 - Weidner, Steffen
T1 - Influence of Electric Field Strength and Emitter Temperature on Field Desorption Mass Spectra of Polyethylene Oligomers
N2 - The influence of electric field strength and emitter temperature on dehydrogenation and CC cleavage in field desorption (FD) mass spectrometry of polyethylene (PE) oligomers of average molecular weights ranging from 500 to 2000 is examined. Low mass oligomers yield molecular weight (MW) distributions that are basically in accordance with results from gel-permeation chromatography. For these materials, dehydrogenation can be greatly reduced by reduction of the emitter potential. Furthermore, the influence of emitter potential on MW distributions indicates the occurrence of field-induced CC cleavages. Reliable MW distributions are more difficult to obtain from higher mass oligomers by FD-MS because of the need for higher field strength and higher emitter temperatures to effect their desorption/ionization. Experiments reveal that the application of FD-MS to PE oligomers is limited not only by field-induced but also by thermally-induced fragmentations. Even then, FD mass spectra contain valuable information on mass range and homogeneity of PE samples up to about m/z 3600.
PY - 2000
DO - https://doi.org/10.1255/ejms.300
SN - 1469-0667
SN - 1356-1049
SN - 1365-0718
IS - 6
SP - 11
EP - 17
PB - IM Publications
CY - Chichester
AN - OPUS4-11098
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI von geregelten und ungeregelten Polyamiden nach kritischer Chromatographie
T2 - VII. Anwendertreffen MALDI-TOF-MS zur Charakterisierung von synthetischen Polymeren
CY - Berlin, Germany
DA - 2002-05-14
PY - 2002
AN - OPUS4-11136
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Mechanism of homogeneously catalyzed polymerization of liquid-crystalline sidegroup monomers investigated by means of MALDI-TOF-MS (No. 433)
T2 - 219th ACS National Meeting
CY - San Francisco, CA, USA
DA - 2000-03-26
PY - 2000
AN - OPUS4-11314
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Beispiele für zweidimensionale Kopplungen von Chromatographie und MALDI-TOF-Massenspektrometrie zur Analyse von Polymeren
T2 - BAM-Abt. VI-Seminar
CY - Berlin, Germany
DA - 2003-09-25
PY - 2003
AN - OPUS4-11139
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - SFC of new liquid-crystalline cholesteryl esters
T2 - InCom '96, International Symposium on Instrumentalized Analytical Chemistry and Computer Technology
CY - Düsseldorf, Germany
DA - 1996-03-25
PY - 1996
AN - OPUS4-11194
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - You, Zengchao
A1 - Jakubowski, Norbert
A1 - Panne, Ulrich
A1 - Weidner, Steffen
T1 - Separation of polystyrene nanoparticles with different coatings using two-dimensional off-line coupling of asymmetrical flow field flow fractionation and capillary electrophoresis
N2 - The successful off-line coupling of asymmetrical flow field flow fractionation (AF4) and capillary electrophoresis (CE) for separation of nanoparticles (NPs) with different surface coatings was shown. We could successfully demonstrate that, in a certain NP size range, hyphenation of both techniques significantly improved the separation of differently coated NPs. Three mixtures of polystyrene nanoparticles (PS-NPs) with comparable core sizes but different coatings (no coating/carboxyl-coated) were studied. Separation in either method resulted in non-baseline resolved or non-separated peaks. In contrast, two-dimensional off-line coupling of AF4 and CE resulted in clearly separated regions in their 2 D plots in case of 20 and 50 nm particle mixtures, whereas the 100 nm NP mixture could not be separated at all. Various factors affecting the separation like hydrodynamic diameter or SDS concentration were discussed.
KW - Capillary electrophoresis (CE)
KW - Nanoparticles with same nominal diameter
KW - Surface coating
KW - Two-dimensional off-line coupling
KW - Asymmetrical flow field flow fractionation (AF4)
PY - 2019
DO - https://doi.org/10.1016/j.chroma.2019.01.056
VL - 1593
SP - 119
EP - 126
PB - Elsevier
AN - OPUS4-47363
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - El Malah, T.
A1 - Rolf, Simone
A1 - Weidner, Steffen
A1 - Thünemann, Andreas
A1 - Hecht, S.
T1 - Amphiphilic folded dendrimer discs and their thermosensitive self-assembly in water
N2 - Folded dendrimers with peripheral ether side chains show a thermally induced hierarchical aggregation process, in which the transition temperature and the dimensions of the aggregates can readily be tuned via the generation number (see figure).
KW - Click chemistry
KW - Cotton effect
KW - Dendrimers
KW - Hierarchical self-assembly
KW - Thermochemistry
PY - 2012
DO - https://doi.org/10.1002/chem.201200414
SN - 0947-6539
SN - 1521-3765
VL - 18
IS - 19
SP - 5837
EP - 5842
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-25822
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - Polymer characterization using sophisticated liquid chromatographic techniques combined with MALDI- and ESI-TOF mass spectrometry
T2 - 55th ASMS conference on Mass Spectrometry
CY - Indianapolis, IN, USA
DA - 2007-06-03
PY - 2007
AN - OPUS4-14745
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - LC-MALDI coupling for the analysis of polymers
T2 - National Meeting of the Centre National de la Recherche Scientifique (CNRS)
CY - Strasbourg, France
DA - 2004-06-03
PY - 2004
AN - OPUS4-11308
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Thünemann, Andreas
A1 - Rolf, Simone
A1 - Knappe, Patrick
A1 - Weidner, Steffen
T1 - In Situ Analysis of a Bimodal Size Distribution of Superparamagnetic Nanoparticles
N2 - The dispersed iron oxide nanoparticles of ferrofluids in aqueous solution are difficult to characterize due to their protective polymer coatings. We report on the bimodal size distribution of superparamagnetic iron oxide nanoparticles found in the MRI contrast agent Resovist, which is a representative example of commercial nanoparticle-based pharmaceutical formulations. The radii of the majority of the nanoparticles (>99%) range from 4 to 13 nm (less than 1% of the particles display radii up to 21 nm). The maxima of the size distributions are at 5.0 and 9.9 nm. The analysis was performed with in situ characterization of Resovist via online coupling of asymmetrical flow field-flow fractionation (A4F) with small-angle X-ray scattering (SAXS) using a standard copper X-ray tube as a radiation source. The outlet of the A4F was directly coupled to a flow capillary on the SAXS instrument. SAXS curves of nanoparticle fractions were recorded at 1-min time intervals. We recommend using the A4F-SAXS coupling as a routine method for analysis of dispersed nanoparticles with sizes in the range of 1-100 nm. It allows a fast and quantitative comparison of different batches without the need for sample preparation.
PY - 2009
DO - https://doi.org/10.1021/ac802009q
SN - 0003-2700
SN - 1520-6882
VL - 81
IS - 1
SP - 296
EP - 301
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-18658
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Knappe, Patrick
A1 - Bienert, Ralf
A1 - Weidner, Steffen
A1 - Thünemann, Andreas
T1 - Poly(acrylic acid): A combined analysis with field-flow fractionation and SAXS
N2 - Polyelectrolytes such as PAA and its salts are widely used, but are notoriously difficult to characterize due to their polyelectrolyte properties and broad molecular mass distributions. In this paper, we report on a new PAA analysis by combining asymmetrical flow field-flow fractionation and an advanced SAXS technique using an acoustic levitator to minimize background scattering. The proof-of-principle is demonstrated with a mixture of three standard PAAs with different molecular masses. Detailed information on the PAA fractions is available on radii of gyration, polymer contour lengths, and coil conformation. Our method is expected to be applicable for a wide range of water-soluble synthetic and natural polymers and ideal for molecular masses of 5 × 103–2 × 105 g · mol-1.
KW - Fractionation of polymers
KW - Molar mass distribution
KW - Polyelectrolytes
KW - Small-angle X-ray scattering
KW - Water-soluble polymers
PY - 2010
DO - https://doi.org/10.1002/macp.201000163
SN - 1022-1352
SN - 1521-3935
VL - 211
IS - 19
SP - 2148
EP - 2153
PB - Wiley-VCH Verl.
CY - Weinheim
AN - OPUS4-22005
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI Imaging MS von Polymeren
T2 - BRUKER-Anwendertreffen
CY - Kassel, Germany
DA - 2011-03-21
PY - 2011
AN - OPUS4-23603
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Chatti, S.
A1 - Weidner, Steffen
A1 - Fildier, A.
A1 - Kricheldorf, H.R.
T1 - Copolyesters of isosorbide, succinic acid, and isophthalic acid: biodegradable, high Tg engineering plastics
N2 - Isosorbide, succinyl chloride and isophthaloyl chloride are polycondensed under various reaction conditions. The heating in bulk with or without catalysts as well in an aromatic solvent without catalyst, and polycondensation with the addition of pyridine only yield low molar mass copolyesters. However, heating in chlorobenzene with addition of SnCl2 or ZnCl2 produces satisfactory molar masses. The number average molecular weights (Mn) of most copolyesters fall into the range of 7000–15,000 Da with polydispersities (PD) in the range of 3–9. The MALDI-TOF mass spectra almost exclusively displayed peaks of cyclics indicating that the chain growth was mainly limited by cyclization and not by side reactions, stoichiometric imbalance or incomplete conversion. The glass-transition temperatures increased with the content of isophthalic acid from 75 to 180 °C and the thermo-stabilities also followed this trend.
KW - Biodegradable
KW - Cyclization
KW - Cyclopolymerization
KW - Isophthalic acid
KW - Isosorbide
KW - Polycondensation
KW - Polyesters
KW - Renewable resources
KW - Succinic acid
PY - 2013
DO - https://doi.org/10.1002/pola.26635
SN - 0360-6376
SN - 0887-624X
VL - 51
IS - 11
SP - 2464
EP - 2471
PB - Wiley
CY - Hoboken, NJ
AN - OPUS4-28577
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
T1 - SnOct 2-Catalyzed Syntheses of Cyclic Poly (l-lactide) s with Catechol as Low-Toxic Co-catalyst
N2 - Polymerizations of l-lactide in bulk at 160 or 180 °C were performed with 1/1 mixtures of catechol (CA) or 4-tert-butylcatechol (BuCA) and tin(II)-2-ethylhexanoate (SnOct2) as catalysts and a variation of the Lac/Cat ratio. Weight average molar masses (Mw) up to 170,000 g mol−1 were obtained with CA and up to 120,000 g mol−1 with BuCA. The cyclic structure of the resulting poly(l-lactide)s was proven by MALDI-TOF mass spectrometry and by comparison of their hydrodynamic volumes with those of commercial linear poly(l-lactide)s. The predominance of even-numbered cycles increased with lower temperatures and shorter polymerization times. This fnding indicates that the cyclic architecture is the results of a ring-expansion polymerization mechanism. Addition of silylated BuCA as co-catalyst was less favorable than addition of free BuCA.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
KW - Catalyst
KW - Catechol
KW - Toxicity
PY - 2019
DO - https://doi.org/10.1007/s10924-019-01545-5
SP - 10924
PB - Springer
AN - OPUS4-49210
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lüdecke, Nils
A1 - Weidner, Steffen
A1 - Schlaad, Helmut
T1 - Poly(2‐oxazoline) s Based on Phenolic Acids
N2 - A series of phenolic-acid-based 2-oxazoline monomers with methoxysubstituted phenyl and cinnamyl side chains is synthesized and polymerized in a microwave reactor at 140 °C using methyl tosylate as the initiator. The obtained poly(2-oxazoline)s are characterized by NMR spectroscopy, MALDITOF mass spectrometry, and size-exclusion chromatography (SEC). Kinetic studies reveal that the microwave-assisted polymerization is fast and completed within less than ≈10 min for low monomer-to-initiator ratios of ≤25.
Polymers with number-average molar masses of up to 6500 g mol−1 and low dispersity (1.2–1.3) are produced. The aryl methyl ethers are successfully cleaved with aluminum triiodide/N,N′ diisopropylcarbodiimide to give a poly(2-oxazoline) with pendent catechol groups.
KW - 2-oxazoline
KW - Catechol
KW - Cationic ring opening polymerization
KW - Microwave
KW - Phenolic acid
PY - 2019
DO - https://doi.org/10.1002/marc.201900404
SP - 1900404
PB - Wiley VCH-Verlag
AN - OPUS4-49396
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Weidner, Steffen
T1 - MALDI-TOF MS und MALDI-MSI zur Identifikation und Klassifizierung von Pollen
N2 - Es werden die letzten Ergebnisse präsentiert, die es ermöglichen, einzelne Pollenkörner unterschiedlicher Arten in Mischungen mittels MALDI-TOF Massenspektrometrie bzw. MALDI-TOF Imaging zu messen und unter Zuhilfenahme multivariater Auswertemethoden zu klassifizieren.
T2 - 24. Bruker MALDI Anwendertreffen
CY - Leipzig, Germany
DA - 18.02.2019
KW - MALDI-TOF Massenspektrometrie
KW - Pollenkörner
KW - Klassifizierung
KW - MALDI Imaging
KW - Multivariate Analyse
PY - 2019
AN - OPUS4-47441
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zeegers, G. P.
A1 - Steinhoff, R. F.
A1 - Weidner, Steffen
A1 - Zenobi, R.
T1 - Evidence for laser-induced redox reactions in matrix-assisted laserdesorption/ionization between cationizing agents and target plate material: a study with polystyrene and trifluoroacetate salts
N2 - Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is often applied to assess the dispersity and the end groups of synthetic polymers through the addition of cationizing agents. Here weaddress how these cation adducts are formed using polystyrene (PS) as a model polymer. We analyzed PSby MALDI-MS with a 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) as the matrix and a range of trifluoroacetate (TFA) salts as cationizing agents on a range of different targetplate materials (copper, 1.4301 stainless steel, aluminum, Inconel 625, Ti90/Al6/V4 and chromium-, gold-and silver-plated stainless steel). It was found that on a stainless steel substrate the metal cations Al+,Li+, Na+, Cu+and Ag+formed polystyrene adducts, whereas K+, Cs+, Ba2+, Cr3+, Pd2+, In3+, or their lower oxidation states, did not. For the copper and silver substrates, PS and DCTB adduct formation with cations liberated from these target plate materials was observed upon addition of a cationizing agent, which indicates the occurrence of redox reactions between the added TFA salts and the target plate material. Judging from their standard electrode potentials, these redox reactions would not normally occur, i.e.,they require an additional energy input, strongly suggesting that the observed redox reactions are laser-induced. Furthermore, copper granules were found to successfully sequester PS from a tetrahydrofuran(THF) solution, consistent with the view complex formation with the copper target plate can take place prior to the MALDI-MS measurement.
KW - Polymer MALDI
KW - Cationization
KW - Polystyrene
KW - Laser-induced redox reactions
KW - Target plate material
PY - 2017
DO - https://doi.org/10.1016/j.ijms.2016.10.007
SN - 1387-3806
SN - 1873-2798
VL - 416
SP - 80
EP - 89
PB - Elsevier B.V.
AN - OPUS4-41146
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H. R.
T1 - The Role of Transesterification in SnOct 2 - Catalyzed Polymerizations of Lactides
N2 - l-lactide or meso-lactide are polymerized either at 120 °C where the polymerization process of l-lactide is accompanied by crystallization, or at 180 °C where poly(l-lactide) remains in the molten state. Polymerizations at 120 °C initially yield even-numbered chains (with respect to lactic acid units) having relatively low dispersity, but the fraction of odd-numbered chains increases with time and the entire molecular weight distribution changes. Traces of cyclics are only formed after 7 d. Polymerizations at 180 °C yield equilibrium of even and odd-numbered chains from the beginning, but at low monomer/initiator ratios and short reaction times (<4 h) cyclics are again not formed. They appear at longer reaction times and entail higher dispersities. The results are discussed in terms of five different transesterification mechanisms.
KW - Polylactides
KW - MALDI
KW - Transesterification
KW - Sn catalysts
PY - 2017
DO - https://doi.org/10.1002/macp.201600331
SN - 1022-1352
VL - 218
IS - 3
SP - 1600331
PB - Wiley
AN - OPUS4-39753
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -