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.

中文翻译：

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高摩尔质量环状聚（L-丙交酯）通过与环状二丁基锡双酚盐的扩环聚合反应

以氧化二丁基锡和 2,2'-二羟基联苯或 2,2'二羟基（1,1'-联萘）为原料制备了两种新型催化剂（SnNa 和 SnBi）。这些催化剂能够在 160 或 180 °C 下快速聚合 L-丙交酯，从而几乎完全形成环状聚丙交酯。这些聚合反应没有外消旋化并产生重均分子量 (Mw's) 高达 140 000 g mol-1 的聚（L-丙交酯）。正如对扩环聚合 (REP) 所预期的那样，Mw 随 Lac/Cat 比率变化很小。在 140、120 和 102 °C 下进行大量聚合，产生具有较低分子量的环状聚丙交酯。在 102 °C 下，以 SnNa 作为催化剂发现偶数循环的强优势。SnNa 还可以催化醇引发的 ROP，产生不含环的线性聚（L-丙交酯）。