TY - JOUR A1 - Weidner, Steffen A1 - Meyer, A. A1 - Falkenhagen, Jana A1 - Kricheldorf, H. R. T1 - Polycondensations and Cyclization of Poly(L-lactide) Ethyl Esters in the Solid State T2 - Polymer Chemistry N2 - The usefulness of seven different Tin catalysts, Bismuth subsalicylate and Titan tetra(ethoxide) for the polycondensation of ethyl L-lactate (ELA) was examined at 150 °C/6 d. Dibutyltin bis(phenoxides) proved to be particularly effective. Despite the low reactivity of ELA, weight average molecular masses (Mw) up to 12 500 were found along with partial crystallization. Furthermore, polylactides (PLAs) of similar molecular masses were prepared via ELA-initiated ROPs of L-lactide by means of the four most effective polycondensation catalysts. The crystalline linear PLAs were annealed at 140 or 160 °C in the presence of these catalysts. The consequences of the transesterification reactions in the solid PLAs were studied by means of matrix-assisted laser desorption/ionization (MALDI TOF) mass spectrometry, gel permeation chromatography (GPC) and small-angle X-ray scattering (SAXS). The results indicate that polycondensation and formation of cycles proceed in the solid state via formation of loops on the surface of the crystallites. In summary, five different transesterification reactions are required to explain all results. PB - RSC Publ. CY - Cambridge KW - Polylactide KW - MALDI-TOF MS KW - Crystalinity PY - 2024 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/59293 AN - OPUS4-59293 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-592934 SN - 1759-9962 VL - 15 IS - 2 SP - 71 EP - 82 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany