TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Meyer, A. T1 - About the Influence of (Non-)Solvents on the Ring Expansion Polymerization of l-Lactide and the Formation of Extended Ring Crystals T2 - Macromolecular Chemistry and Physics N2 - Ring-expansion polymerizations (REPs) catalyzed by two cyclic tin catalysts(2-stanna-1.3-dioxa-4,5,6,7-dibenzazepine [SnBiph] and 2,2-dibutyl-2-stanna-1,3-dithiolane [DSTL) are performed at 140 °C in bulk. Small amounts (4 vol%) of chlorobenzene or other solvents are added to facilitate transesterification reactions (ring–ring equilibration) in the solid poly(l-lactide)s. In the mass range up to m/z 13 000 crystalline PLAs displaying a so-called saw-tooth pattern in the MALDI-TOF mass spectra are obtained indicating the formation of extended-ring crystals. The characteristics of extended-ring crystallites and folded-ring crystallites are discussed. Furthermore, extremely high melting temperatures (Tm’s up to 201.2 °C) and melting enthalpies (𝚫Hm’s up to 106 J g−1)) are found confirming that 𝚫Hmmax, the 𝚫Hm of a perfect crystal, is around or above 115 J g−1 in contrast to literature data. PB - Wiley VHC-Verlag KW - Polylactide KW - MALDI-TOF MS KW - Ring-expansion polymerization KW - Crystals PY - 2022 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/56503 AN - OPUS4-56503 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565038 SN - 1022-1352 SP - 1 EP - 8 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany