TY - JOUR A1 - Kricheldorf, Hans A1 - Weidner, Steffen T1 - High molar mass cyclic poly(L-lactide) via ring-expansion polymerizationwith cyclic dibutyltin bisphenoxides T2 - European Polymer Journal N2 - Two new catalysts (SnNa and SnBi) were prepared from dibutyltin oxide and 2,2′-dihydroxybiphenyl or2,2′dihydroxy(1,1′-binaphtyl). These catalysts enabled rapid polymerizations of L-lactide at 160 or 180 °C in bulk, whereby almost exclusively cyclic polylactides were formed. These polymerizations were free of racemization and yielded pol(L-lactide)s having weight average molecular weights (Mw's) up to 140 000 g mol−1. The Mw's varied little with the Lac/Cat ratio as expected for a ring expansion polymerization (REP). Polymerizations performed in bulk at 140, 120 and 102 °C yielded cyclic polylactides with lower molecular weights. At 102 °C a strong predominance of even-numbered cycles was found with SnNa as catalyst. SnNa can also catalyze alcohol-initiated ROPs yielding linear poly(L-lactide) free of cyclics. PB - Elsevier Ltd. KW - MALDI-TOF MS KW - Polylactide KW - Ring-opening Polymerization KW - Cyclization KW - Catalysts PY - 2018 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/45439 AN - OPUS4-45439 SN - 0014-3057 SN - 1873-1945 VL - 105 SP - 158 EP - 166 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany