中文摘要：

以乙醇铁、正丁醇铁为催化剂，研究了在丙交酯／醇铁的聚合体系中引人羟基化合物催化丙交酯开环聚合的机理。羟基化合物为苄醇时，聚合产物分子是以苄氧基和乳酰基为端基的聚乳酸（PLA），聚合产物的分子量受丙交酯／苄醇摩尔投料比控制；当羟基化合物为聚乙二醇（PEG）时，聚合产物的分子结构为PLA-PEG-PLA的三嵌段共聚物，分子链的端基结构均为乳酰基结构单元，聚合产物的LA／PEG摩尔比与投料比基本一致，醇铁在其中起促进PEG参与聚合成酯的作用。这些结果表明在含羟基化合物的丙交酯／醇铁聚合体系中，羟基化合物作为共引发剂参与了丙交酯的开环聚合。在聚合过程中，羟基化合物首先与醇铁作用形成一种复合物，在这种复合物作用下，丙交酯的酰氧键断裂，按配位一插入机理进行增长。

英文摘要：

The ring-opening polymerization mechanism of lactide in the presence of hydroxyl compounds was studied by using ferric ethoxide and ferric n-butoxide as catalysts respectively. I H NMR analysis showed that polylactide （PLA） with benzyloxy and lactyl end groups was produced when benzyl alcohol was introduced into the lactide/ alkoxide polymerization system. The molecular weight of the product depended on the molar ratio of lactide/benzyl alcohol. In the presence of polyethylene glycol （PEG） for the lactide/alkoxide systems, a triblock copolymer PLA- PEG-PLA with lactyl end groups was obtained and the molar ratio of lactide/PEG of the copolymer was basically agreed with the results calculated according to the feed molar ratio. The ferric alkoxides promoted PEG participating in the ring-opening polymerization of lactide and esterification. According to the above results, it was suggested that the hydroxyl compounds acted as co-initiators in the ferric alkoxide/lactide polymerization system. In the polymerization process they first formed complexes with ferric alkoxides, which attacked the lactide carbonyl carbon and the acyl-oxygen bond cleaved because of its being weakened and then the ring-opening polymerization of lactide proceeded via a coordination-insertion mechanism.