Synthesis of high-molecular-weight poly(L-lactic acid) by direct polycondensation

Abstract

Full Paper: To prepare poly(lactic acid) (PLA) with improved mechanical properties, high-molecular-weight poly(L-lactic acid) (PLLA) was synthesized by the direct polycondensation of lactic acid in solution phase. During polymerization, the molecular weight of PLA was influenced by the water content present in the solution; thus, the experimental apparatus was designed to remove the water efficiently and this study was focused on the optimization of the polymerization conditions such as polymerization time, solvent, and kinds of catalyst, etc. Additionally, to search for a good catalyst in the polymerization, the mixed oxide catalysts were synthesized by sol-gel method and it was characterized by XRD and BET. The results show that the (M) over bar (v) of PLA obtained was about 33 000, when 0.2 wt.-% of SnCl2.2H(2)O was used as a catalyst in the polymerization. The DSC study shows that the thermal properties of PLA such as T-g and T-m were influenced by the kind of solvent as well as the molecular weight of PLA.