Effects of Introduction of L-Lactide on Microstructures, Thermal Properties and In vitro Degradation of Poly(glycolide-co-ε-caprolactone) Block Copolymer

Abstract

In this study, poly(glycolide-co—caprolactone) (PGCL) block copolymers, which have an ABA block structure, were prepared by a two-step polymerization process, and their microstructures, thermal properties and in vitro degradation properties according to introducing a small amount of L-lactide as a comonomer in the first step of the polymerization process were systematically investigated. Through our study, it was confirmed that the introduction of L-lactide in the first step of the polymerization process had a great effect on the microstructure of the random PGCL prepolymer (B block) as well as the final PGCL block copolymer (ABA block). Specifically, with the introduction of L-lactide, the average sequence length of glycolide segments on the PGCL prepolymer decreased from 3.32 to 2.40. In addition, it was observed that there is a relatively large difference in the average sequence length of glycolide segments in the final PGCL block copolymers. As a result, these microstructural changes of the PGCL prepolymer originated from the L-lactide comonomer affected significantly the thermal properties and in vitro degradation properties on the final PGCL block copolymers. Compared with the PGCL block copolymer without L-lactide, melting temperature and crystallization temperature of the PGCL block copolymer with L-lactide decreased, as well as their thermal degradation temperature. In addition, the introduction of a small amount of L-lactide comonomer accelerated the hydrolytic degradation of the PGCL block copolymer. Overall, by introducing L-lactide copolymer in the first step of the two-step manufacturing process for the PGCL block copolymer, changes of various properties on the PGCL block copolymer originated from the changes in the microstructure of random PGCL prepolymer were confirmed.