Abstract
An A-B-A block copoly (ester-ether) comprising poly(L-lactic acid) (A) and poly (oxyethylene) (B) was prepared by copolymerization of L-lactide and a commercially available telechelic polymer, polyethylene glycol (PEG), with different molecular weights by the catalysis of triethyl aluminium/toluene. The molecular weight and the unit composition were successfully controlled by changing the L-lactide/PEG ratio in feed. DSC curves of the copolymers are ascribed to the endothermic peak with PEG segment and exothermic peak by PLLA segment. There is a tendency that melting temperature ($T_m$) reduced with increasing PEG composition. These results suggested that the PEG segments and PLLA are compatible and homogeneously mixed in the amorphous phase of PLLA without forming a microphase separation in the solid state. The compatibility of both polymers, however, would not be so high as to prevent crystallization of PLLA. It was found that the copolymer films showed an improved flexibility due to the incorporation of the soft PEG segment. The in vitro hydrolysis test of the films showed that the block copolymer has much higher degradability than the homo poly(L-lactic acid)