Synthesis and Characterization of Biodegradable Random Copolymers of L-Lactide, Glycolide and Trimethylene Carbonate

Random copolymers of L-lactide, glycolide and trimethylene carbonate were synthesized by bulk ring-opening copolymerization of monomers in the presence of stannous octoate as catalyst at 120ºC for 48 h. Glycolide and L-lactide were prepared from their parent acids and then purified by multiple recrystallizations from ethyl acetate. Six copolymers with various mole% of the monomers were prepared and characterized. 1H NMR and 13C NMR spectra of copolymers that were recorded show the random character of the materials. Each 1H NMR and 13C NMR signal split to several peaks. Thermal behaviours of the copolymers were evaluated by DSC thermograms. Copolymers that contain L-lactide and trimethylene carbonate show an endotherm in DSC, but those containing three monomers do not show any transition in DSC. Mechanical properties of the copolymers were evaluated by measuring stress-strain curves of film specimens prepared by solvent casting.