HYDROLYTIC DEGRADATION OF ALIPHATIC POLYESTERS COPOLYMERIZED WITH POLY(ETHYLENE GLYCOL)S

Poly(1,4-butanediol succinate) copolymers were prepared by melt polyco ndensation of succinic acid and 1,4-butanediol with 10-50 mol% (in fee d) of poly(ethylene glycol) (PEG), where molecular weight (MW) of PEG is 200-2000. The reduced specific viscosity of the copolymers increase d with incorporation of the PEG component, but a higher PEG content in the copolymers reduced it. The temperature of melting (T-m) and cryst allinity decreased with increasing PEG content. T-m depression of the copolymers followed approximately Flory's equation, suggesting that th ese are random type copolymers. Tensile strength and elongation decrea sed with increasing MW and content of PEG. The weight loss of copolyme r films in a buffer solution with or without lipase at 37 degrees C, a s well as water absorption, increased with increasing PEG content, imp lying that higher water absorption contributes to hydrolytic degradati on of the films. However, the weight loss of copolymers with PEG of lo wer MW increased greatly in spite of lower water absorption, demonstra ting that hydrolytic degradation is influenced by the concentration of degradable ester linkages between succinic acid and PEG segments rath er than water absorption.