Physical properties of high molecular weight 1,3-trimethylene carbonate and D,L-lactide copolymers

High molecular weight statistical copolymers of 1,3-trimethylene carbonate (TMC) and D,L-lactide (DLLA) were synthesized and characterized with the aim of assessing their potential in the development of degradable and flexible materials for application in the biomedical field. Under the applied polymerization conditions (130 degrees C, 3 days using stannous octoate as a catalyst) monomer conversion was high or almost complete, and high molecular weight polymers (M(n) above 170 000) were obtained. Significant improvement of the mechanical performance of these materials was observed in comparison to results previously reported for TMC and DLLA based copolymers of lower molecular weight. For the entire range of compositions the polymers are amorphous with a glass transition temperature ranging between -17 degrees C for poly(TMC) and 53 degrees C for poly(DLLA). The polymers vary from rubbers to stiff materials as the content of TMC decreases. All polymers are hydrophobic with very low equilibrium water absorption (<1.5 wt %). Thermal analyses and tensile tests were performed on polymer samples after water uptake. Due to a plasticizing effect of the water, the thermal properties, and consequently the mechanical performance, of the copolymers with higher content of DLLA were the most affected. After water absorption, the polymer mechanical behavior can change from glassy to rubbery, as observed for the copolymer with 80 mol % of DLLA. The obtained results suggest that these copolymers are promising candidates as biomaterials in the preparation of degradable medical devices and systems.