TY - JOUR A1 - Kricheldorf, H. A1 - Scheliga, F. A1 - Weidner, Steffen T1 - Syntheses of Cyclic Poly(l-lactide)s by Means of Zinc-Based Ring-Opening Polymerization with Simultaneous Polycondensation (ROPPOC) Catalysts T2 - Macromolecular Chemistry and Physics N2 - Ring-opening polymerizations of l-lactide are studied in bulk at 140 or 160 °C with zinc n-hexanoate, zinc 4-chlorothiophenolate, and zinc pentafluoro thiophenolate (ZnSPF) as catalysts. The reactivity increases in the given order. With all three catalysts a high fraction of cycles is obtained only at polymerization (annealing) times around 7 d. With ZnSPF weight average molecular weights (Mw) up to 178 000, a Tm around 199 °C and a 𝚫Hm around 99 J g−1 were achieved. The samples annealed for 4 or 7 d also display a saw tooth pattern of the mass peak distribution in the matrix-assisted laser desorption/ionization time of flight spectra indicating transesterification reactions across the surface of extended ring crystals. This process optimizes the thermodynamical properties of the crystalline cyclic polylactides and is responsible for the high Tm and 𝚫Hm values. PB - Wiley VHC-Verlag KW - Polylactide KW - MALDI-TOF MS KW - Ring opening polymerization KW - Polymerization PY - 2023 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/57826 AN - OPUS4-57826 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-578264 SN - 1022-1352 SP - 202300070 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany