Study on the preparation and properties of lactic acid based copolymer

A new process to prepare L-lactic acid based polymer with high molecular-weight was established. In this process, the carboxyl terminated poly (L-lactic acid) (PLLA) prepolymer was first synthesized via polycondensation of L-lactic acid and a little adipic acid, and then the molecular weight of PLLA was increased by a chain-extending reaction using bisphenol-A epoxy resin as a chain extender. In situ FTIR was used to characterize the activity of reaction between epoxy groups at the end of bisphenol-A epoxy resin and carboxyl groups at the end of PLLA prepolymer, and the results showed that the reaction was of high activity. The weight-average molecular weight of prepared L-lactic acid based copolymer (PLLA-co-BisA ER) was up to 210,000 at an optimum synthetic condition. The thermal property and crystallization behavior of prepared copolymer were also studied.