Molten Ring-Open Copolymerization of L-Lactide and Cyclic Trimethylene Carbonate *

The biodegradable poly(l-lactide-co-trimethylene carbonate) [poly(LLA-co-TMC)] was synthesized by molten ring-open copolymerization and the structure and properties of the copolymer were investigated by gel permeation chromatography (GPC), NMR, FTIR, differential scanning calorimeter (DSC), and Instron testing. The copolymer with a higher l-lactide (LLA) content had a higher initial molecular weight (M _n), but a lower final M _n. In contrast, the copolymer with a higher trimethylene carbonate (TMC) content had a lower initial M_n , but its M_n increased with increasing reaction time and TMC content. The glass transition temperature (T_g ), the melting temperature (T_m ) and the crystallinity of the copolymer decreased with increasing TMC content. The elongation of the copolymer significantly increased with increasing TMC content while the toughness passed through a maximum.