Synthesis and characterization of novel biodegradable copolyesters by transreaction of poly(ethylene terephthalate) with copoly(succinic anhydride/ethylene oxide)

Poly(ethylene terephthalate)/copoly(succinic anhydride/ethylene oxide) copo lymers, (PET/PES copolymers) were synthesized by the transreaction between PET and PES and characterized with GPC, H-1 NMR, and DSC.,. Most of the cop olymers obtained were random copolymers. The films cast of these copolymers were transparent. The thermal, mechanical properties, and biodegradability of the copolymers obtained were studied with respect to the composition an d lengths of aliphatic and aromatic units in the copolymers. In the copolym ers having high PET content, the melting points, due to the PET segment, we re observed by DSC measurement, although the fusion heats of the copolymers were small. The enzymatic hydrolyzability by a lipase from Rhizopus arrhiz us and biodegradability by activated sludge of the copolymers decreased wit h an increase in PET content. When the length of succinic acid unit in the copolymer was below 2, the hydrolyzability of the copolymers decreased cons iderably. The tensile strengths of the cast films prepared from the copolym ers synthesized by the transreaction increased with an increase in PET cont ent, whereas, the elongations at break decreased. Their tensile strengths w ere half, and the elongations were double compared to those of PET homopoly mer film. (C) 2000 John Wiley & Sons, Inc.