L-lactide ring open polymerization with catalyst based on calcium compounds

The bulk ring opening polymerization of L-lactide using calcium methoxide and calcium octoate as catalysts at different lactide/calcium (LA:Ca) molar ratio was investigated. The reactions were carried out at LA:Ca ratio of 100, 250, 500, 1,000 and 5,000 at 180 deg C. The poly(L-lactic acid) (PLLA) were characterized according the molecular weight, microstructure and thermal properties. Higher polymerization yields was 66 wt % in the LA:Ca ratio= 100. The polydispersity ranged from 1.20 to 1.44 and the molecular weight varied from 8,500 to 19,500. Results of X-ray diffraction indicated that the polymers present high crystallinity, particularly the PLLA obtained with LA:Ca molar ration= 1,000 and 5,000. (author)