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.