Syntheses and Physical Properties of Novel Optically Active Poly(ester−carbonate)s by Copolymerization of Substituted Trimethylene Carbonate with ε-Caprolactone and Their Biodegradation Behavior

This paper describes the synthesis and the biodegradation of optically active copolymers, poly[( R )-1-methyltrimethylene carbonate- co -ε-caprolactone] and poly[( S )-1-methyltrimethylene carbonate- co -ε-caprolactone] and poly[( R, R )-1,3-dimethyltrimethylene carbonate- co -ε-caprolactone] and poly[( S, S )-1,3-dimethyltrimethylene carbonate- co -ε-caprolactone]. The copolymers were prepared using a novel organolanthanide or AlEt 3 −H 2 O as the polymerization initiators, and their biodegradation by various enzymes and acclimated activated sludges was studied as a function of their composition, stereochemistry, crystallinity, T g (glass transition temperature), T m (melting point), molecular weight, and polydispersity. The copolymers synthesized exhibited high molecular weights with rather narrow molecular weight distributions and produced thermoplastic films when ( R )-1-MTC (1-MTC = 1-methyltrimethylene carbonate) or ( R, R )-1,3-DTC (1,3-DTC = 1,3-dimethyltrimethylene carbonate) content is less than 50 mol %. Optically active and racemic copolymers prepared using 1-MTC/CL (CL = ε-caprolactone) ratios of 17/83 to 19/81 were effectively biodegraded by lipoprotein lipase, cholesterol esterase and activated sludge. For the copolymers prepared using various 1,3-DTC/CL ratios, the poly( rac- 1,3-DTC- co -CL) was biodegraded faster than the poly[( R, R )-1,3-DTC- co- CL] and poly[( S, S )-1,3-DTC- co -CL] copolymers regardless of the 1,3-DTC/CL ratio. Biodegradation of all of these copolymers generated numerous cavities on the outermost surface of polymer films or solid masses without changing their molecular weight and polydispersity.