Diblock copolymerizations of L- or D,L-lactide (LA) with trimethylene carbonate (TMC) or 2,2-dimethyltrimethylene carbonate (2,2-DTMC) with SmMe(C5Me5)(2)- (tetrahydrofuran) as an initiator and triblock copolymerizations Of L- or D,L-LA/cyclic carbonates/L- or D,L-LA with [SM(C5Me5)(2)](2)(PhC=C=C=CPh) as an initiator generated the desired block copolymers. This article describes the comparison of biodegradabilities by proteinase K and a compost and mechanical properties between the resulting di- or triblock copolymers and random copolymers composed of L- or D,L-LA and cyclic carbonates. The scanning electron microscopic profiles of resulting polymers were measured to understand the morphological change during biodegradation. (C) 2003 Wiley Periodicals, Inc.