TY - JOUR A1 - Weidner, Steffen A1 - Kricheldorf, H. R. A1 - Scheliga, F. T1 - Ring-expansion copolymerization of L-lactide and glycolide T2 - Macromolecular Chemistry and Physics N2 - 1:1 Copolymerizations of glycolide (GL) and L-lactide (LA) is performed in bulk at 100°C and at 160°C with four cyclic tin catalysts. The resulting copolyesters are characterized by SEC measurements, 1H and 13C NMR spectroscopy and by MALDI TOF mass spectrometry. At 160°C and longer reaction time (22 h) nearly complete conversion of both monomers is achieved, and cyclic copolymers with nearly random sequences are formed. At shorter times (0.5-3.0 h, depending on catalyst) the conversion of LA is incomplete, and only cyclics having even numbers of lactyl units are obtained. At 100°C at 22 h again cycles mainly consisting of even numbered lactyl units are formed, but with even and odd numbers of glycolyl units. Copolymerization of lactide at 160°C with small amounts of GL show that formation of high Tm crystallites (Tm > 190°C) is hindered even when only > 2% of GL is added. For polyglycolide containing a smaller amount of lactide complete solubility in hexafluoroisopropanol is only observed around and above 20 mol% of lactide. PB - WileyVCH KW - Ring-expansion polymerization KW - Copolymerization KW - MALDI-TOF MS KW - L-lactide KW - Glycolide KW - Crystallization PY - 2021 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/52027 AN - OPUS4-52027 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520270 SN - 1022-1352 VL - 22 IS - 3 SP - 307 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany