Preparation and characterization of high molecular weight poly(L-lactic-glycolic acid) copolymer

High molecular weight poly(L-lactic-glycolic acid)(PLGA) was successfully synthesized by chain extension of hydroxyl terminated prepolymer(OLGA-OH) with 1,6-hexamethylene diisocyanate(HDI) as the chain extender.The impact of HDI dosage on the molecular weight and property of the chain extended product PLGA was investigated.The structure and properties were characterized using Fourier transform infrared spectroscopy(FT-IR),gel permeation chromatography(GPC),differential scanning calorimetry(DSC),thermal gravimetric analysis(TGA) and nuclear magnetic resonance(NMR).The results showed that the obtained PLGA appeared the best chain extension result and had the maximum molecular weight with Mn of 5.6×104 and Mw of 15.0×104 when n(—NCO)/n(—OH)=2∶1.The glass transition temperature of the PLGA was increased from 36 ℃ to 53 ℃ after chain extension.