Study On Degrad Ability Of Poly(L-Lactic-Co-Glycolicacid)Copolymer

In this thesis, a series of low molecular weight pre-polymers(OLGA-OH), consisting of L-lactic acid (L-LA) and glycolic acid (GA)(L-LA/GA=80/20,60/40,50/50, molar ratio), were prepared via melt polycondensation using SnCl2·2H2O and toluenesulfonic acid (TSA) as the catalysts, using1,4-butanediol (BD) as blocking agent. A series of PLGA which are nontoxic, with good biocompatibility and a high molecular weight have been successfully synthesized via chain-extension reaction using aliphatic1,6-hexamethylene diisocyanate (HDI) as the chain extender, PLLA was prepared in the same method.In this work, PLGA and PLLA films which are prepared by solvent-cast method were incubated in phosphate buffered saline solution in pH7.2-7.4at37℃to investigate their vitro degradation behaviors. The change of molecular weight, weight loss, composition and thermal properties of the samples were characterzed by potentiometry, otentiometry, gel permeation chromatography(GPC), scanning electron microscopy(SEM), nuclear magnetic resonance (’H-NMR) and differential scanning calorimeter (DSC). The degradation mechanism of PLLA and PLGA was analysed.In this paper, we examined the effects of composition of copolymers on the degradation behaviors of the PLGA films. Results indicate that the degradation rate of PLGA could be adjusted by controlling the compositions of the copolymer and increasing the glycolide content. The degradation rate of PLGA with more glycolide content is faster than that with less glycolide content. PLGA50/50is the fastest, and PLLA is the slowest. In this work, we give a reference for the development and application of PLGA and PLLA materials, particularly in the medicine fields.