Investigation of Silyl-Amide Complexes as Catalysts for the Ring-Opening Polymerization of L-Lactide

摘要

A series of silyl-amide complexes (= M{N(SiMe3)2}2) were examined as the catalysts for the ring-opening polymerization of L-lactide. The poly(L-lactic acid) (PLLA) synthesized with the Zn complex showed a M_n near the theoretical value with narrow dispersity. The Zn complex without 1-dodecanol added also gave a poly(L-lactic acid) with M_n near 10,000 Da, although its molecular weight distribution was wide. The poly(L-lactic acid) obtained with the Sn complex in the absence of 1-dodecanol had a M_n higher than 40,000 Da, suggesting that the Sn catalyst involved in the insertion reaction with lactide should have higher activity for the polymerization. This steric space makes the coordination of L-lactide easier and causes faster rate of conversion in the early stage of the polymerization despite its small polarization.