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 C–C 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 C–C 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 - 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 - 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 helix–coil 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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: Me2SnCl2120 °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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - Kricheldorf, Hans A1 - Weidner, Steffen T1 - About the influence of salicylic acid on tin(II)octanoate-catalyzed ring opening polymerizationof L-lactide N2 - L-Lactide was polymerized in bulk with tin(II)2-ethylhexanoate SnOct2) as catalyst and salicylic acid as cocatalyst. The Lac/Cat ratio, Cocat/Cat ratio, temperature and time were varied. Increasing Cocat/Cat ratios reduced both,polymerization rate and molecular weight. However,under optimized conditions high molar mass (Mw up to 178,000), colorless, cyclic polylactides were formed in a short time. A few polymerizations performed at 160 and 180°C with the combination of SnOct2 and silylated salicylic acid gave similar results. Neat tin II) salicylate was prepared from SnOct2 and used for REPs of L-lactide in bulk, but the results were not better than those obtained from combinations of SnOct2 and salicylic acid. Furthermore, dibutyltin salicylate was synthesized and used as catalyst for polymerizations of L-lactide in bulk at temperatures varying from 102 to 160°C. Cyclic polylactides with Mw’s up to 40,000 were the main reaction products. At 100–102°C a predominance of odd-numbered cycles was found proving a REP mechanism. KW - Polylactide KW - MALDI-TOF MS KW - Cyclization KW - Catalyst KW - Ring-opening polymerization PY - 2019 DO - https://doi.org/10.1016/j.eurpolymj.2019.07.003 VL - 119 SP - 37 EP - 44 PB - Elsevier Ltd. AN - OPUS4-49211 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 fiber–epoxy 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 fiber–epoxy 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 - 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 - 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 - Scholz, Philipp A1 - Wachtendorf, Volker A1 - Panne, Ulrich A1 - Weidner, Steffen ED - Scholz, Philipp T1 - Degradation of MDI-based polyether and polyester-polyurethanes in various environments - Effects on molecular mass and crosslinking N2 - Size-exclusion chromatography (SEC) was used to monitor changes of the molecular masses of thermoplastic polyether – and polyester urethane (TPU) exposed to thermal, hydrolytic, and photo-oxidative (UV) Degradation conditions for several days. The thermal treatment was performed at elevated temperatures (100–200 °C) under oxidative (air) as well as non-oxidative (nitrogen) conditions to evaluate the specific influence of oxygen on the degradation. At higher temperatures (≥175 °C) a fast decrease of the molecular masses of both PU accompanied by a high degree of crosslinking was found. At lower temperatures (≤150 °C) the polymers remained widely unaffected by thermal degradation within the investigated degradation interval of up to two weeks. Surprisingly, the influence of oxygen (air) was found to be less distinct. In contrast to that, UV treatment at 25 °C at less than 10% rel. humidity (RH) resulted in a fast crosslinking, whereas the molecular masses of both PU decreased slower than for thermal treatments. The depth of penetration of the UV radiation was estimated using 3D printed PU samples with different thicknesses. Hydrolysis based degradation effects were less significant. Only slight molecular mass changes were detected at temperatures ≤80 °C within a time span of 14 days, while no crosslinking could be measured. Considering the degradation results at the investigated exposure parameters, it could be shown that esterbased PU in general exhibits a significant higher stability compared to ether-based materials. KW - Polyurethane KW - Thermal degradation KW - UV degradation KW - Molecular masses KW - Crosslinking PY - 2019 UR - https://www.sciencedirect.com/science/article/pii/S0142941819302363 DO - https://doi.org/10.1016/j.polymertesting.2019.04.028 SN - 0142-9418 VL - 77 SP - 105881, 1 EP - 12 PB - Elsevier CY - Amsterdam AN - OPUS4-48619 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 - 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 - 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 - 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 - 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 - 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 - 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 - Soulis, S. A1 - Triantou, D. A1 - Weidner, Steffen A1 - Falkenhagen, Jana A1 - Simitzis, J. T1 - Structural analysis of biodegradable low-molecular mass copolyesters based on glycolic acid, adipic acid and 1,4 butanediol and correlation with their hydrolytic degradation N2 - Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, their in vitro hydrolytic degradation was studied and correlated with their structure. The hydrolytic degradation of the copolyesters was directly related with the degree of crystallinity and the diameter of the crystallites. It was found that glycolate units disturb the ordering of the butylene adipate units, which results in a decrease of the crystallinity. By comparing the hydrolysis parameters of synthesized copolyesters with those of similar aliphatic copolyesters a hydrolysis mechanism was proposed. According to this mechanism, the degradation takes place not only by the loss of end units, but also through the removal of larger segments. MALDI-TOF MS data showed that the possibility of a copolyester macromolecule forming cyclic structures correlates with the arrangement of ester groups in the macromolecules and the structure of the linear segments. KW - Biodegradable KW - Biopolymers KW - Hydrolytic degradation KW - Ft-IR KW - Matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry KW - MALDI-TOF-MS PY - 2012 DO - https://doi.org/10.1016/j.polymdegradstab.2012.09.002 SN - 0141-3910 SN - 1873-2321 VL - 97 IS - 11 SP - 2091 EP - 2103 PB - Applied Science Publ. CY - London AN - OPUS4-26723 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 - 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 - 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 - 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 - 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. 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 - 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 - 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 methanol–water 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 isooctane–ethyl 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 - 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 - 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 - 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 nanoparticle’s 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 - 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 - 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 - 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, 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 - 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 - 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 - 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 - 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 A1 - Scheliga, F. T1 - Poly(Epsilon-caprolactone) by combined ring-opening polymerization and azeotropic polycondensation - The role of cyclization and equilibration N2 - Using three different catalysts, water-initiated polymerizations of ε-caprolactone were conducted in bulk with variation of the monomer/water ratio. The resulting CH2OH and CO2H- terminated polylactones were subjected in situ to azeotropic polycondensations. With Bi-triflate and temperatures, the polycondensations were not much successful and involved side reactions. With ZnCl2, and especially SnCl2, considerably higher molar masses were achieved. The substitution of toluene for chlorobenzene for refluxing gave better results. The polycondensations broadened the molar mass distribution of the ROP-based prepolymers, and polydispersities between 1.4-1.8 were obtained. The MALDI-TOF mass spectra revealed that the polycondensations significantly enhanced the fraction of rings due to efficient 'end-biting' reactions. By comparison with copolymerization experiments and Sn methoxide-initiated polymerizations, it was demonstrated that equilibration reactions, such as the formation of rings by 'back-biting,' did not occur. KW - Ring-opening polymerization KW - Epsilon-caprolactone (e-CL) KW - Cyclization KW - MALDI-TOF mass spectrometry KW - Polycondensation KW - Polyesters PY - 2012 DO - https://doi.org/10.1002/pola.26222 SN - 0360-6376 SN - 0887-624X VL - 50 IS - 20 SP - 4206 EP - 4214 PB - Wiley CY - Hoboken, NJ AN - OPUS4-26500 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 - Weidner, Steffen A1 - Falkenhagen, Jana A1 - Breßler, Ingo T1 - Copolymer composition determined by LC-MALDI-TOF MS coupling and 'MassChrom2D' data analysis N2 - The MALDI-TOF MS analysis of copolymers very often results in complex spectra. A chromatographic separation/fractionation prior to the MALDI investigation can be advantageous since the MALDI mass spectra of fractions very often reveal well-resolved peaks of distinguishable copolymer series. For this purpose, different modes of chromatography have been applied. Chromatographic runs were transferred to MALDI targets utilizing a combined air/electrospray deposition device. Using the new MassChrom2D software, fraction-dependent 2D copolymer compositions plots were obtained providing additional information on the chromatographic mode, and enabling fast modification of conditions to increase separation. KW - Copolymer composition KW - Chromatography KW - Coupling KW - MALDI-TOF mass spectrometry PY - 2012 DO - https://doi.org/10.1002/macp.201200169 SN - 1022-1352 SN - 1521-3935 VL - 213 IS - 22 SP - 2404 EP - 2411 PB - Wiley-VCH CY - Weinheim AN - OPUS4-27270 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 - 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 - 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 - Diehn, S. A1 - Zimmermann, B. A1 - Tafintseva, V. A1 - Seifert, S. A1 - Bagcioglu, M. A1 - Ohlson, M. A1 - Weidner, Steffen A1 - Fjellheim, S. A1 - Kohler, A. A1 - Kneipp, Janina T1 - Combining Chemical Information From Grass Pollen in Multimodal Characterization N2 - The analysis of pollen chemical composition is important to many fields, including agriculture, plant physiology, ecology, allergology, and climate studies. Here, the potential of a combination of different spectroscopic and spectrometric methods regarding the characterization of small biochemical differences between pollen samples was evaluated using multivariate statistical approaches. Pollen samples, collected from three populations of the grass Poa alpina, were analyzed using Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, surface enhanced Raman scattering (SERS), and matrix assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). The variation in the sample set can be described in a hierarchical framework comprising three populations of the same grass species and four different growth conditions of the parent plants for each of the populations. Therefore, the data set can work here as a model system to evaluate the classification and characterization ability of the different spectroscopic and spectrometric methods. ANOVA Simultaneous Component Analysis (ASCA) was applied to achieve a separation of different sources of variance in the complex sample set. Since the chosen methods and sample preparations probe different parts and/or molecular constituents of the pollen grains, complementary information about the chemical composition of the pollen can be obtained. By using consensus principal component analysis (CPCA), data from the different methods are linked together. This enables an investigation of the underlying global information, since complementary chemical data are combined. The molecular information from four spectroscopies was combined with phenotypical information gathered from the parent plants, thereby helping to potentially link pollen chemistry to other biotic and abiotic parameters. KW - Pollen KW - MALDI-TOF MS KW - FTIR KW - Raman KW - Multivariate analyses PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-504822 DO - https://doi.org/10.3389/fpls.2019.01788 VL - 10 SP - 1788 AN - OPUS4-50482 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 - 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 - 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 - 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 -