TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Scheliga, F. T1 - Cyclic Polylactides via Simultaneous Ring-Opening Polymerization and Polycondensation Catalyzed by Dibutyltin Mercaptides T2 - Journal of Polymer Science A - Polymer Chemistry N2 - L-Lactide is polymerized in bulk at 160 8C either with dibutyltin bis(benzylmercaptide) (SnSBzl), dibutyltin bis(benzothiazole 2-mercaptide) (SnMBT), or with dibutyltin bis(pentafluorothiophenolate) (SnSPF) as catalysts. SnSBzl yields linear polylactides having benzylthio-ester end groups in addition to cyclic polylactides, whereas SnMBT and SnSPF mainly or exclusively yield cyclic polylactides. This finding, together with model reactions, indicates that the SnS catalysts promote a combined ring-opening polymerization and polycondensation process including end-to-end cyclization. SnMBT caused slight racemization (3%–5%), when used at 160 8C. With SnSPF optically pure cyclic poly(L-lactide)s with high-molecular weights can be prepared at 160 8C. PB - Wiley Periodicals KW - Cyclopolymerization KW - Catalysts KW - MALDI-TOF MS KW - Polyester KW - Ring-opening polymerization PY - 2017 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/42600 AN - OPUS4-42600 VL - 55 IS - 22 SP - 3767 EP - 3775 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany