Star-shaped poly[(trimethylene carbonate)-co-(epsilon-caprolactone)] and its block copolymers with lactide/glycolide:synthesis, characterization and properties

Linear and star-shaped copolymers of trimethylene carbonat/epsilon-caprolactone were synthesized using different polyol initiators and catalysts. Unexpectedly, when dipentaerythritol was used as an initiator cross-linked rubbers were obtained, that swell in chlorofonn. This network formation can be understood by 'in situ' generation of cross-linker molecules from trimethylene carbonate and initiator tor. SEC analysis showed that with D-sorbitol star-shaped copolymers are synthesized with an average functionality between 4 and 6. These low molecular weight rubbers were used as a macro-initiator for the subsequent lactide/ glycolide polymerization. Star-shaped lactide/glycolide block copolymers with a poly[(trimethylene carbonate)co-(epsilon-caprolactone)] rubber core based on D-sorbitol show good mechanical properties. At relatively low rubber content ductile tensile behavior was observed indicating extensive toughening

SUPERTOUGH POLY(LACTIDE)S

Semi-crystalline and amorphous copolymers of lactide and glycolide were rubber modified with degradable rubbers based on epsilon-caprolactone. The influence of crystallinity of the matrix, type of rubber and chain architecture on the impact resistance of the resulting materials was investigated. With a poly(L-lactide-co-epsilon-caprolactone) rubber semi-crystalline poly(lactide)s could be impact modified to a greater extent than amorphous non-crystallizable lactide matrices. Poly(trimethylene carbonate-co-epsilon-caprolactone) was used in blends and linear and star-shaped block copolymers which yield supertough materials that do not break in Izod notched impact testing. Rubber content appears critical around 20 weight percent, where a sharp transition is observed