Direct synthesis with melt polycondensation and microstructure analysis of poly(L-lactic acid-co-glycolic acid)

High-molecular-weight poly((L)-lactic acid-co-glycolic acid) (PLGA) was prepared through melt polymerization from glycolic acid (GA) and (L)-lactic acid ((L)-LA) and then characterized. High resolution H-1 and C-13 NMR were performed for microstructure analysis of polymer. The solubility in chloroform, compositions, and sequence lengths of PLGA suggest higher reactivity of GA compared with (L)-LA and shortening GA blocks with reaction time. The racemization of (L)-LA blocks and transesterification in PLGA are enhanced by increase of GA fractions. PLGA (90/10) samples show crystallization of relatively long (L)-LA sequences in copolymer chains and the absence of the crystallization of GA blocks. All these results demonstrate the influence of racemization and transesterification on the microstructure of PLGA.