TY - JOUR A1 - Kricheldorf, H. R. A1 - Meyer, A. A1 - Weidner, Steffen T1 - High Tm Poly(l-lactide)s by Means of Bismuth Catalysts? N2 - One series of BiSub-catalyzed ring-opening polymerizations (ROPs) is per-formed at 160 °C for 3 days with addition of difunctional cocatalysts to find out, if poly(l-lactide) crystallizes directly from the reaction mixture. An analogous series is performed with monofunctional cocatalysts. High Tm crystal-lites (Tm > 190 °C) are obtained from all bifunctional cocatalysts, but not from all monofunctional ones. It is shown by means of SAXS measurements that the high Tm values are mainly a consequence of a transesterification–homogenization process across the lamellar surfaces resulting in thickness and smoothing of the surfaces. An unusual enthalpy-driven modification of the molecular weight distribution is found for samples that have crystallized during the polymerization. A third series of ROPs is performed at 170 °C for 2 h followed by annealing at 120 °C (2 h) to induce crystallization. Complete transformation of the resulting low Tm crystallites (Tm < 180 °C) into the high Tm crystallites by annealing at 170 °C for 1 d is not achieved, despite variation of the cocatalyst. KW - Polylactide KW - MALDI-TOF MS KW - Crystallization PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-522777 DO - https://doi.org/10.1002/macp.202100019 SN - 1022-1352 VL - 222 IS - 8 SP - 19 PB - Wiley AN - OPUS4-52277 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - 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 - 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 - Rosemann, Paul A1 - Müller, Christina A1 - Meyer, A. A1 - Halle, T. T1 - Influence of nitrogen on the corrosion resistance of martensitic stainless steels N2 - The corrosion resistance of martensitic stainless steels (MSS) depends strongly on the chemical composition and the applied heat treatment. Both determines the distribution of the alloying elements in the microstructure and the resulting material properties. The addition of nitrogen is known to be beneficial for the pitting corrosion resistance of stainless steels. In case of MSS this effect is not only connected to nitrogen itself because nitrogen can be used to substitute carbon which also influences the result of the heat treatment process. This paper shows the effect of nitrogen on the corrosion resistance in relation to the hardening process of MSS. Therefore the effects of austenitization duration, austenitization temperature and cooling rate on microstructure, hardness and corrosion resistance were studied on the MSS X30CrMoN15 1 and X50CrMoV15. The effect of different cooling rates was studied in the range of > 100 K/s down to 1 K/s using the jominy end quench test. The changes in corrosion resistance were detected with electrochemical potentiodynamic reactivation (EPR) and by the determination of critical pitting potentials. Besides this experimental approach thermodynamic calculations with the software thermocalc will be presented and used for the interpretation of the effect of nitrogen on the corrosion resistance of MSS. T2 - 18th Chemnitz Seminar on Materials Engineering – 18. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany KW - Martensitic stainless steels KW - Corrosion resistance KW - Heat treatment PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-366956 DO - https://doi.org/10.1088/1757-899X/118/1/011002 VL - 118 IS - 1 SP - 19 EP - 19 PB - IOP Publishing AN - OPUS4-36695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rosemann, Paul A1 - Müller, C. A1 - Meyer, A. A1 - Halle, T. ED - Lampke, T. ED - Wagner, G. ED - Wagner, M.F.-X. T1 - Einfluss von Stickstoff auf Mikrostruktur und Korrosionsverhalten martensitischer nichtrostender Stähle N2 - Die Korrosionsbeständigkeit martensitischer nichtrostender Stähle (MNS) wird wesentlich von der chemischen Zusammensetzung und dem Wärmebehandlungszustand beeinflusst. Beides bestimmt die Verteilung der Legierungselemente im Gefüge und die daraus resultierenden Werkstoffeigenschaften. Das Legieren mit Stickstoff bewirkt im Allgemeinen eine Verbesserung der Lochkorrosionsbeständigkeit von nichtrostenden Stählen. Bei martensitischen nichtrostenden Stählen ist dieser Effekt nicht nur auf den Stickstoffgehalt selbst zurückzuführen, sondern auch auf den gleichzeitig verringerten Kohlenstoffgehalt, der ebenfalls das Ergebnis der Wärmebehandlung beeinflusst. In dieser Arbeit wird der Einfluss von Stickstoff auf die Korrosionsbeständigkeit in Bezug zum Härtungsprozess von MNS dargestellt. Dazu wird vergleichend der Effekt von Austenitisierungsdauer, -temperatur und Abkühlgeschwindigkeit auf Gefüge, Härte und Korrosionsbeständigkeit der MNS X50CrMoV15 und X30CrMoN15 1 untersucht. Die Abkühlgeschwindigkeit wurde mit dem Stirnabschreckversuch gezielt variiert, um den Einfluss von Abkühlgeschwindigkeiten von > 100 K/s bis 1 K/s zu charakterisieren. Die Veränderungen der Korrosionsbeständigkeit werden durch die elektrochemisch potentiodynamische Reaktivierung (EPR) und durch die Bestimmung kritischer Lochkorrosionspotentiale dokumentiert. Neben diesem experimentellen Ansatz werden auch die Ergebnisse von thermodynamischen Berechnungen mit der Software Thermocalc vorgestellt und abschließend auch zur Interpretation des Einflusses von Stickstoff auf die Korrosionsbeständigkeit martensitischer nichtrostender Stähle genutzt. T2 - 18. Werkstofftechnisches Kolloquium der TU Chemnitz CY - Chemnitz, Germany DA - 10.03.2016 KW - Korrosionsbeständigkeit KW - Corrosion resistance KW - Wärmebehandlung KW - Heat treatment KW - Nichtrostende Stähle KW - Stainless steels KW - Thermocalc KW - Thermocalc PY - 2016 SN - 978-3-00-052212-3 SN - 1439-1597 VL - 59 SP - 325 EP - 336 PB - TU Chemnitz, Fakultät für Maschinenbau, Institut für Werkstoffwissenschaft und Werkstofftechnik CY - Chemnitz AN - OPUS4-37263 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Griesche, Axel A1 - Engelhardt, M. A1 - Kargl, F. A1 - Meyer, A. A1 - Weis, H. A1 - Yang, F. T1 - Diffusion measurements with neutron radiography KW - Diffusion KW - Metal KW - Semiconductor KW - Melt KW - In-situ KW - Radiography KW - Darken KW - Capillary PY - 2009 IS - Chapter 4.1.5 SP - 214 EP - 215 AN - OPUS4-21449 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Meyer, A. A1 - Kricheldorf, H. R. T1 - Ring–Ring Equilibration in Solid, Even-Numbered Cyclic Poly(l-lactide)s and their Stereocomplexes N2 - Even-numbered cyclic poly(d-lactide) and poly(l-lactide) are prepared by ringexpansion polymerization. The cyclic pol(l-lactide) is annealed either at 120 or at 160 °C for several days. The progress of transesterification in the solid state is monitored by the formation of odd-numbered cycles via matrix-assisted laser desorption/ionization-time of flight mass spectrometry. The changes of the crystallinity are monitored by differential scanning calorimetry, wideand small-angle x-ray scattering (WAXS and SAXS) measurements. Despite total even-odd equilibration at 160 °C, the crystallinity of poly(l-lactide) is not reduced. Furthermore, the crystallinity of the stereocomplexes of both cyclic polylactides do not decrease or vanish, as expected, when a blocky or random stereosequence is formed by transesterification. This conclusion is confirmed by 13C NMR spectroscopy. These measurements demonstrate that transesterification is a ring–ring equilibration involving the loops on the surfaces of the lamellar crystallites thereby improving crystallinity and 3D packing of crystallites without significant broadening of the molecular weight distribution. KW - Polylactide KW - MALDI-TOF MS KW - Cyclization PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506458 DO - https://doi.org/10.1002/macp.202000012 VL - 221 IS - 9 SP - 2000012 PB - Wiley-VCH Verlag AN - OPUS4-50645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Meyer, A. T1 - High Tm poly(L-lactide)s via REP or ROPPOC of L-lactide N2 - A new kind of high melting (HTm) pol(L-lactide) was discovered when cyclic poly(L-lactide)s were prepared by ring-expansion polymerization with cyclic tin catalysts at 130–160 °C in bulk. By DSC measurements with 10 K min−1 melting temperatures (Tm) in the range of 190–196 °C were found. The WAXS and SAXS measurements evidenced that not a new crystal lattice but a well-ordered morphology and a higher perfection of the crystallites are responsible for the high Tm values and high crystallinities. Under identical reaction conditions SnOct2-catalyzed and alcohol-initiated ROPs do not yield these crystallites. Furthermore, it was found that the standard crystallites are kinetically favored upon rapid crystallization, whereas the high melting form of poly(L-lactide) is thermodynamically more stable. KW - Polylactide KW - MALDI-TOF MS KW - ROPPOC PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-507477 DO - https://doi.org/10.1039/c9py01908a VL - 11 IS - 12 SP - 2182 EP - 2193 PB - Royal Society of Chemistry AN - OPUS4-50747 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jain, V. A1 - Kjaervik, Marit A1 - Bahr, S. A1 - Dietrich, P. A1 - Meyer, M. A1 - Thissen, A. A1 - Linford, M. R. T1 - Bovine serum albumin, aqueous solution, by near-ambient pressure XPS N2 - Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show survey, C 1s, O 1s, and N 1s narrow scans from an aqueous solution of a common protein, bovine serum albumin. The C 1s peak envelope is well fit to four symmetric peaks of equal width that correspond to carbon bonded to carbon and hydrogen (C-1), carbon singly bonded to oxygen (C-2), carbonyl and/or amide carbon (C-3), and carboxyl carbon (C-4). Two possible peak fits are considered for the N 1s and O 1s peak envelopes. The N 1s signal is fit to four peaks that correspond to amine (—NH2), Amide (OvCZNH2), ammonium (—NH3 +), and N2(g) nitrogen, and alternatively to three peaks that correspond to amine, amide, and N2(g) nitrogen. The O 1s peak envelope is similarly fit to three and four components. KW - NAP-XPS KW - BSA KW - Bovine serum albumin KW - XPS KW - Near-ambient pressure PY - 2019 DO - https://doi.org/10.1116/1.5055229 VL - 26 IS - 1 SP - 014027 PB - American Vacuum Society CY - New York, USA AN - OPUS4-48655 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Meyer, A. A1 - Chatti, S. A1 - Kricheldorf, H. R. T1 - About the transformation of low Tm into high Tm poly(L-lactide)s by annealing under the influence of transesterification catalysts N2 - Cyclic polylactides were prepared in bulk at 170 °C, crystallized at 120 °C and then annealed at temperatures between 130 and 170 C with variation of catalyst, catalyst concentration and annealing time. The transformation of the initially formed low melting (LTm) crystallites, having melting temperatures (Tm) <180 °C into high melting (HTm) crystallites having Tm values > 189 °C was monitored by means of DSC measurements and characterized in selected cases by SAXS measurements. It was confirmed that the formation of HTm crystallites involves a significant growth of the thickness of the lamellar crystallites along with smoothing of their surface. Annealing at 170 °C for 1 d or longer causes thermal degradation with lowering of the molecular weights, a gradual transition of cyclic into linear chains and a moderate decrease of lamellar thickness. An unexpected result revealed by MALDI TOF mass spectrometry is a partial reorganization of the molecular weight distribution driven by a gain of crystallization enthalpy. KW - Polylactide KW - MALDI-TOF MS KW - Crystallization KW - Annealing PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521062 DO - https://doi.org/10.1039/d0ra10012a VL - 11 IS - 5 SP - 2872 EP - 2883 PB - Royal Society of Chemistry AN - OPUS4-52106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meyer, A. A1 - Weidner, Steffen A1 - Kricheldorf, H. T1 - Stereocomplexation of cyclic polylactides with each other and with linear poly(L-lactide)s N2 - Two kinds of cyclic poly(D- and L-lactide)s were synthesized, namely CI labeled samples mainly consisting of even-numbered cycles with low dispersity and CII, CIII or CIV-labeled ones consisting of equal amounts of even and odd-numbered cycles with high dispersity and igher molecular weights (Mw up to 300 000). Furthermore, linear poly L-lactide)s were prepared by initiation with ethanol and in both series the molecular weight was varied. The formation of stereocomplexes from cyclic poly(D-lactide)s and all kinds of poly L-lactide)s was performed in dichloromethane/toluene mixtures. The stereocomplexes crystallized from the reaction mixture were characterized in the virgin state and after annealing at 205 °C. Stereocomplexes free of stereohomopolymers with crystallinities up to 80% were obtained from all experiments in yields ranging from 60 to 80%. Despite the high annealing temperature (maintained for 1 h), little transesterification was observed and the crystallinity slightly increased. KW - Polylactide KW - MALDI-TOF MS KW - Stereocomplex KW - Cyclic PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-496693 DO - https://doi.org/10.1039/c9py01236b VL - 10 SP - 6191 EP - 6199 PB - Royal Society for Chemistry AN - OPUS4-49669 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Meyer, A. T1 - High Tm linear poly(L-lactide)s prepared via alcohol-initiated ROPs of L-lactide N2 - Alcohol-initiated ROPs of L-lactide were performed in bulk at 160 °C for 72 h with variation of the catalyst or with variation of the initiator (aliphatic alcohols). Spontaneous crystallization was only observed when cyclic Sn(II) compounds were used as a catalyst. Regardless of initiator, high melting crystallites with melting temperatures (Tm) of 189–193 °C were obtained in almost all experiments with Sn(II) 2,2′-dioxybiphenyl (SnBiph) as catalyst, even when the time was shortened to 24 h. These HTm poly(lactide)s represent the thermodynamically most stable form of poly(L-lactide). Regardless of the reaction conditions, such high melting crystallites were never obtained when Sn(II) 2-ethylhexanoate (SnOct2) was used as catalyst. SAXS measurements evidenced that formation of HTm poly(L-lactide) involves growth of the crystallite thickness, but chemical modification of the crystallite surface (smoothing) seems to be of greater importance. A hypothesis, why the “surface smoothing” is more effective for crystallites of linear chains than for crystallites composed of cycles is discussed. KW - Polylactide KW - MALDI-TOF MS KW - Ring-opening polymerization PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524330 DO - https://doi.org/10.1039/d1ra01990b VL - 11 IS - 23 SP - 14093 EP - 14102 PB - Royal Society of Chemistry AN - OPUS4-52433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, M. A1 - Drenkova-Tuhtan, A. A1 - Szczerba, Wojciech A1 - Gellermann, C. A1 - Meyer, C. A1 - Steinmetz, H. A1 - Mandel, K. A1 - Sextl, G. T1 - Nanostructured ZnFeZr oxyhydroxide precipitate as efficient phosphate adsorber in waste water: understanding the role of different material-building-blocks N2 - In the recent years great effort has been made to find materials and technologies for removing and recycling phosphate from waste water. We herein present the detailed study on a nanostructured multicomponent material, which turned out to be a very efficient phosphate adsorber. The role of each constituent is carefully examined to understand the collaborative interaction of the components of the nanostructured adsorber. We found evidence that it is particularly the nanostructure of this material, which has a crucial influence on the phosphate Adsorption performance, indicating a synergetic effect of the different components. Moreover, the adsorption mechanism was studied dependent on the concentration of phosphate, changing from a Freundlich/Langmuir-like behaviour to a BET-like multilayer adsorption of phosphate on the material. Our work demonstrates that there is high potential for discovering new adsorber materials for environmental applications through careful engineering of the chemical composition in close connection with the materials (nano) structure. KW - Adsober KW - Phosphate adsorption KW - Waste water treatment PY - 2017 DO - https://doi.org/10.1039/c6en00507a SN - 2051-8153 SN - 2051-8161 VL - 4 IS - 1 SP - 180 EP - 190 PB - RSC AN - OPUS4-39700 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeynalov, Eldar A1 - Wagner, M. A1 - Friedrich, Jörg Florian A1 - Magerramova, M. A1 - Salmanova, N. A1 - Hidde, Gundula A1 - Meyer-Plath, A. T1 - The peculiar behavior of functionalized carbon nanotubes in hydrocarbons and polymeric oxidation environments N2 - It has been shown that selected types of substituents are able to vary the oxidative behavior of multi-walled carbon nanotubes. Such substituents investigated were sterically hindered secondary amino groups bonded in grafted piperidine units and covalently bonded bromine groups. Their interference and activity was preliminary determined in the model cumene and then in oil diesel fraction and low density polyethylene oxidation reactions. Results obtained indicate that chemical linking of amine moieties containing –NH groups directly to the carbon nanotubes core significantly increases their intrinsic anti-oxidative capacity while the grafting of Br-groups provokes the opposite functioning of the pristine samples. This inference was proved by thermogravimetric and differential thermal analysis of the polyethylene composites and experiments on profound aerobic oxidation of petroleum naphthenic fraction derived from the commercial Baku oils blend diesel cut. KW - Multi-walled carbon nanotubes KW - Amine derivatives KW - Plasma-chemical technique KW - Brominated carbon nanotubes KW - Rate of model oxidation KW - Anti-oxidative efficiency KW - Catalytic activity KW - Inhibition rate constant KW - Photoelectron spectroscopy KW - Oxidation KW - Polyethylene composites KW - Oil diesel fraction PY - 2016 DO - https://doi.org/10.1080/01694243.2016.1239304 SN - 0169-4243 SN - 1568-5616 VL - 31 IS - 9 SP - 988 EP - 1006 AN - OPUS4-39894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Oprzeska-Zingrebe, E. A. A1 - Meyer, Susann A1 - Roloff, Alexander A1 - Kunte, Hans-Jörg A1 - Smiatek, J. T1 - Influence of compatible solute ectoine on distinct DNA structures: thermodynamic insights into molecular binding mechanisms and destabilization effects N2 - In nature, the cellular environment of DNA includes not only water and ions, but also other components and co-solutes, which can exert both stabilizing and destabilizing effects on particular oligonucleotide conformations. Among them, ectoine, known as an important osmoprotectant organic co-solute in a broad range of pharmaceutical products, turns out to be of particular relevance. In this article, we study the influence of ectoine on a short single-stranded DNA fragment and on double-stranded helical B-DNA in aqueous solution by means of atomistic molecular dynamics (MD) simulations in combination with molecular theories of solution. Our results demonstrate a conformation-dependent binding behavior of ectoine, which favors the unfolded state of DNA by a combination of electrostatic and dispersion interactions. In conjunction with the Kirkwood–Buff theory, we introduce a simple Framework to compute the influence of ectoine on the DNA melting temperature. Our findings reveal a significant linear decrease of the melting temperature with increasing ectoine concentration, which is found to be in qualitative agreement with results from denaturation experiments. The outcomes of our Computer simulations provide a detailed mechanistic rationale for the surprising destabilizing influence of ectoine on distinct DNA structures. KW - Ectoine KW - DNA KW - Thermodynamic KW - Melting temperature PY - 2018 DO - https://doi.org/10.1039/c8cp03543a SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 40 SP - 25861 EP - 25874 PB - Royal Society of Chemistry AN - OPUS4-46327 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 - Weidner, Steffen A1 - Meyer, A. A1 - Kricheldorf, H. T1 - Cyclic polyglycolides via ring-expansion polymerization with cyclic tin catalysts N2 - Glycolide was polymerized in bulk with two cyclic catalysts − 2,2-dibutyl-2-stanna-1,3-dithiolane (DSTL) and 2-stanna-1,3-dioxa-4,5,6,7-dibenzepane (SnBiph). The monomer/initiator ratio, temperature (140 – 180 °C) and time (1–––4 days) were varied. The MALDI TOF mass spectra exclusively displayed peaks of cyclic polyglycolide (PGA) and revealed an unusual “saw-tooth pattern” in the mass range below m/z 2 500 suggesting formation of extended ring crystallites. The DSC measurements indicated increasing crystallinity with higher temperature and longer time, and after annealing for 4 d at 160 °C a hitherto unknown and unexpected glass transition was found in the temperature range of 170–185 °C. Linear PGAs prepared by means of metal alkoxides under identical conditions did not show the afore-mentioned features of the cyclic PGAs, neither in the mass spectra nor in the DSC measurements. All PGAs were also characterized by SAXS measurements, which revealed relatively small L-values suggesting formation of thin crystallites in all cases with little influence of the reaction conditions. KW - Polyglycolide KW - MALDI-TOF MS KW - Ring-expansion polymerization KW - Crystals PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595541 DO - https://doi.org/10.1016/j.eurpolymj.2024.112811 SN - 0014-3057 VL - 207 SP - 1 EP - 9 PB - Elsevier Ltd. AN - OPUS4-59554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. A1 - Weidner, Steffen A1 - 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 - Thiele, Isabel A1 - Santolin, Lara A1 - Meyer, Klas A1 - Machatschek, Rainhard A1 - Bölz, Uwe A1 - Tarazona, Natalia A. A1 - Riedel, Sebastian L. T1 - Microbially synthesized poly(hydroxybutyrate-co-hydroxyhexanoate) with low to moderate hydroxyhexanoate content: Properties and applications N2 - Plastic pollution is the biggest environmental concern of our time. Breakdown products like micro- and nanoplastics inevitably enter the food chain and pose unprecedented health risks. In this scenario, bio-based and biodegradable plastic alternatives have been given a momentum aiming to bridge a transition towards a more sustainable future. Polyhydroxyalkanoates (PHAs) are one of the few thermoplastic polymers synthesized 100 % via biotechnological routes which fully biodegrade in common natural environments. Poly(hydroxybutyrate-cohydroxyhexanoate) [P(HB-co-HHx)] is a PHA copolymer with great potential for the commodity polymers industry, as its mechanical properties can be tailored through fine-tuning of its molar HHx content. We have recently developed a strategy that enables for reliable tailoring of the monomer content of P(HB-co-HHx). Nevertheless, there is often a lack of comprehensive investigation of the material properties of PHAs to evaluate whether they actually mimic the functionalities of conventional plastics. We present a detailed study of P(HB-co-HHx) copolymers with low to moderate hydroxyhexanoate content to understand how the HHx monomer content influences the thermal and mechanical properties and to link those to their abiotic degradation. By increasing the HHx fractions in the range of 2 – 14 mol%, we impart an extension of the processing window and application range as the melting temperature (Tm) and glass temperature (Tg) of the copolymers decrease from Tm 165 ◦C to 126 ◦C, Tg 4 ◦C to − 5.9 ◦C, accompanied by reduced crystallinity from 54 % to 20 %. Elongation at break was increased from 5.7 % up to 703 % at 14 mol% HHx content, confirming that the range examined was sufficiently large to obtain ductile and brittle copolymers, while tensile strength was maintained throughout the studied range. Finally, accelerated abiotic degradation was shown to be slowed down with an increasing HHx fraction decreasing from 70 % to 55 % in 12 h. KW - Molecular Biology KW - General Medicine KW - Biochemistry KW - Structural Biology PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595636 DO - https://doi.org/10.1016/j.ijbiomac.2024.130188 VL - 263 SP - 1 EP - 9 PB - Elsevier B.V. AN - OPUS4-59563 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kern, Simon A1 - Wander, Lukas A1 - Meyer, Klas A1 - Guhl, Svetlana A1 - Gottu Mukkula, A. R. A1 - Holtkamp, M. A1 - Salge, M. A1 - Fleischer, C. A1 - Weber, N. A1 - Engell, S. A1 - Paul, Andrea A1 - Pereira Remelhe, M. A1 - Maiwald, Michael T1 - Flexible automation with compact NMR spectroscopy for continuous production of pharmaceuticals N2 - Modular plants using intensified continuous processes represent an appealing concept for the production of pharmaceuticals. It can improve quality, safety, sustainability, and profitability compared to batch processes; besides, it enables plug-and-produce reconfiguration for fast product changes. To facilitate this flexibility by real-time quality control, we developed a solution that can be adapted quickly to new processes and is based on a compact nuclear magnetic resonance (NMR) spectrometer. The NMR sensor is a benchtop device enhanced to the requirements of automated chemical production including robust evaluation of sensor data. Beyond monitoring the product quality, online NMR data was used in a new iterative optimization approach to maximize the plant profit and served as a reliable reference for the calibration of a near-infrared (NIR) spectrometer. The overall approach was demonstrated on a commercial-scale pilot plant using a metal-organic reaction with pharmaceutical relevance. KW - NMR Spectroscopy KW - NIR Spectroscopy KW - Real-time process monitoring KW - Real-time quality control KW - Continuous processes KW - CONSENS KW - Data Fusion PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-480623 DO - https://doi.org/10.1007/s00216-019-01752-y SN - 1618-2642 SN - 1618-2650 VL - 411 IS - 14 SP - 3037 EP - 3046 PB - Springer Nature CY - Heidelberg AN - OPUS4-48062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -