Biodegradable triblock copolymers and implantable medical devices made therefrom

A composition comprising

• a biodegradable triblock copolymer including an A-B-A′ structure wherein the A and A′ blocks each include polylactide, the B block includes from about 55 to about 100 mole percent of polytrimethylene carbonate and 0 to about 45 mole percent polylactide, and the biodegradable triblock copolymer overall includes from about 15 to about 25 mole percent of the polytrimethylene carbonate and from about 75 to about 85 mole percent of the polylactide, and
• an additional biocompatible material.

An implantable medical device comprising:

• at least one filament including a biodegradable triblock copolymer including an A-B-A′ structure wherein the A and A′ blocks each include polylactide, the B block includes from about 55 to about 100 mole percent of polytrimethylene carbonate and 0 to about 45 mole percent polylactide, and the biodegradable triblock copolymer overall includes from about 15 to about 25 mole percent of the polytrimethylene carbonate and from about 75 to about 85 mole percent of the polylactide.

A method of forming a biodegradable triblock copolymer comprising:

• mixing monomer units of trimethylene carbonate and optionally lactide, with at least one first initiator and at least one catalyst in a dry form in a reactor to form a B block of an ABA′ triblock copolymer, and
• mixing monomer units of lactide and at least one second catalyst with the B block to add A and A′ blocks to the B block thereby forming the ABA′ triblock copolymer.