TY - JOUR A1 - Lüdecke, Nils A1 - Weidner, Steffen A1 - Schlaad, Helmut T1 - Poly(2‐oxazoline) s Based on Phenolic Acids N2 - A series of phenolic-acid-based 2-oxazoline monomers with methoxysubstituted phenyl and cinnamyl side chains is synthesized and polymerized in a microwave reactor at 140 °C using methyl tosylate as the initiator. The obtained poly(2-oxazoline)s are characterized by NMR spectroscopy, MALDITOF mass spectrometry, and size-exclusion chromatography (SEC). Kinetic studies reveal that the microwave-assisted polymerization is fast and completed within less than ≈10 min for low monomer-to-initiator ratios of ≤25. Polymers with number-average molar masses of up to 6500 g mol−1 and low dispersity (1.2–1.3) are produced. The aryl methyl ethers are successfully cleaved with aluminum triiodide/N,N′ diisopropylcarbodiimide to give a poly(2-oxazoline) with pendent catechol groups. KW - 2-oxazoline KW - Catechol KW - Cationic ring opening polymerization KW - Microwave KW - Phenolic acid PY - 2019 DO - https://doi.org/10.1002/marc.201900404 SP - 1900404 PB - Wiley VCH-Verlag AN - OPUS4-49396 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - 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 - Kricheldorf, H. R. A1 - Weidner, Steffen T1 - High molar mass cyclic poly(L-lactide)s by means of neat tin (II) 2-ethylhexanoate N2 - L-lactide was polymerized in bulk at 120, 140, 160 and 180°C with neat tin(II) 2-ethylhexanoate (SnOct2) as catalyst. At 180°C the Lac/Cat ratio was varied from 25/1 up to 8 000/1 and at 160°C from 25/1 up to 6 000/1. The vast majority of the resulting polylactides consist of cycles in combination with a small fraction of linear chains having one octanoate and one COOH end group. The linear chains almost vanished at high Lac/Cat ratios, as evidenced by MALDI-TOF mass spectrometry and measurements of intrinsic viscosities and dn/dc values. At Lac/Cat ratios <1000/1 the number average molar masses (Mn) are far higher than expected for stoichiometic initiation, and above 400/1 the molar masses vary relatively little with the Lac/Cat ratio. At 180° slight discoloration even at short times and degradation of the molar masses were observed, but at 160°C or below colorless products with weight average molar masses (Mw) up to 310 000 g mol-1 were obtained. The formation of high molar mass cyclic polylactides is explained by a ROPPOC (Ring-Opening Polymerizatiom with simultaneous Polycondensation) mechanism with intermediate formation of linear chains having one Sn-O-CH end group and one mixed anhydride end group. Additional experiments with tin(II)acetate as catalyst confirm this interpretation. These findings together with the detection of several transesterification mechanisms confirm previous critique of the Jacobson-Stockmayer theory. KW - Polylactide KW - MALDI-TOF MS KW - Cyclization PY - 2020 DO - https://doi.org/10.1039/d0py00811g VL - 11 IS - 32 SP - 5249 EP - 5260 PB - Royal Society for Chemistry AN - OPUS4-51130 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen T1 - The Ring-Opening Polymerisation-Polycondensation (ROPPOC) Approach to cyclic Polymers N2 - A new concept called “Ring-Opening Polymerization (ROP) combined with simultaneous POlyCondensation” (ROPPOC) is presented and discussed. This synthetic strategy is based on the intermediate formation of chains having two end groups that can react with each other. The ROPPOC syntheses are subdivided into three groups according to the nature of the chain ends: two ionic end groups, one ionic and one covalent chain end and a combination of two reactive covalent end groups may be involved, depending on the catalyst. The usefulness for the preparation of cyclic polymers is discussed with a review of numerous previously published examples. These examples concern to following classes of cyclic polymers: polypeptides, polyamides, polyesters, including polycarbonates, and cyclic polysiloxanes. It is demonstrated, that the results of certain ROPPOC syntheses are in contradiction to the Jacobson-Stockmayer theory. Finally, the usefulness of ROPPOCs for the detection of polydisperse catenanes is discussed. KW - Ring-opening Polymerisation KW - MALDI-TOF MS KW - ROPPOC KW - Cyclic PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-508509 DO - https://doi.org/10.1002/marc.202000152 SP - 2000152 PB - Wiley AN - OPUS4-50850 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Scheliga, F. T1 - Synthesis of cyclic polymers and flaws of the Jacobson–Stockmayer theory N2 - Cyclic poly(L-lactide)s were prepared by ring-opening polymerization combined with simultaneous polycondensation (ROPPOC) in bulk at 160 ° with dibutyltin bis(4-cyanophenoxide) as catalyst. It is demonstrated by MALDI TOF mass spectrometry and 1H NMR end group analyses that cycles are formed by endto-end cyclization in addition to “back-biting” transesterification. Formation of high molar mass cyclic poly L-lactide)s by means of several more reactive ROPPOC catalysts presented previously and in new experiments is discussed. These experimental results, together with theoretical arguments, prove that part of the Jacobson–Stockmayer theory is wrong. The critical monomer concentration, above which end-toend cyclization is seemingly impossible, does not exist and reversible like irreversible polycondensations can theoretically proceed up to 100% conversion, so that finally all reaction products will necessarily adopt a cyclic architecture. KW - Polylactide KW - MALDI-TOF MS KW - Cyclization PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506419 DO - https://doi.org/10.1039/d0py00226g VL - 11 IS - 14 SP - 2595 EP - 2604 PB - Royal Society for Chemistry AN - OPUS4-50641 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - 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 - You, Zengchao A1 - Nirmalananthan-Budau, Nithiya A1 - Resch-Genger, Ute A1 - Panne, Ulrich A1 - Weidner, Steffen T1 - Separation of polystyrene nanoparticles bearing different carboxyl group densities and functional groups quantification with capillary electrophoresis and asymmetrical flow field flow fractionation N2 - Two sets of polystyrene nanoparticles (PSNPs) with comparable core sizes but different carboxyl group densities were made and separated using asymmetric flow field flow fractionation (AF4), capillary electrophoresis (CE), and the off-line hyphenation of both methods. Our results revealed the significant potential of two-dimensional off-line AF4-CE hyphenation to improve the separation and demonstrated for the first time, the applicability of CE to determine the functional group density of nanoparticles (NPs). Compared to the result acquired with conductometric titration, the result obtained with synthesized 100 nm sized PSNPs revealed only a slight deviation of 1.7%. Commercial 100 nm sized PSNPs yielded a deviation of 4.6 %. For 60 nm sized PSNPs, a larger deviation of 10.6 % between both methods was observed, which is attributed to the lower separation resolution. KW - Nanoparticle KW - A4F KW - Capillary electrophoresis KW - Carboxyl group PY - 2020 DO - https://doi.org/10.1016/j.chroma.2020.461392 VL - 1626 SP - 461392 PB - Elsevier B.V. AN - OPUS4-51080 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - 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 - Kricheldorf, H. R. A1 - Weidner, Steffen T1 - Reply to the comment on “synthesis of cyclic polymers and flaws of the Jacobson-Stockmayer theory” by R. Szymanski N2 - In a recent publication the authors have presented theoretical and experimental results indicating that the Jacobson–Stockmayer (JS) theory does not provide a correct description of reversible polycondensations for all polymers and for high conversions (e.g. polycondensation in bulk). In this context reversibility means that all condensation step whether resulting in chain growth or in cyclization are reversible and thus, part of an equilibrium. The first two sections of that paper were focused on the demonstration that small, and above all, large cycles can be formed by end-to-end (ete) cyclization in reversible like in irreversible polycondensations. A significant contribution of ete-cyclization to the course of reversible polycondensations was denied by J + S apparently as a contribution to Florýs dogma, that the end groups of long polymer chains will never meet. KW - Polylactide KW - MALDI-TOF MS KW - Jacobsen-Stockmayer theory PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513985 DO - https://doi.org/10.1039/D0PY01118E VL - 11 IS - 38 SP - 6226 EP - 6228 PB - Royal Society of Chemistry AN - OPUS4-51398 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -