The Ring-opening Polymerization Of Lactide And Modification

Because poly lactic acid has excellent biodegradebility, biocompatibility and ease of processing performance advantages of extensive research by the people, therefore PLA is one of the degradation of the polymer prepared raw materials.our main job is synthesis high molecular PLA through ROP of lactide and optimizing reactions. Also basic research of synthesis copolymer(PLA-co-Asp) and st-g-PLA.Firstly, Zinc-base catalyst was synthesized and used succesfully to catalyze the ring-opening polymerization(ROP) of lactide.The effects of molar ratio of monomer and catalyst、the polymerization time and the polymerization temperature on the viscosity molecular weight(Mη) of the polylactide(PLA)obtained from the ROP were studied in detail.In the conditions of monomer and catalyst is100, polymerization time is12h, polymerization temperature is150℃, the viscosity molecular molecular weight of the PLA can be high up to2.84×104.Secondly, Poly(lactide-alt-aspartic acid)(PLA-co-Asp) was obtained by copolymerizing lactide and3-[(benzyloxycarbonyl)methyl]morpholine-2,5-dione which was synthesized via aspartic acid and chloroacetyl chloride as raw material and was characterized by FT-IR,1H-NMR. Effects of the amount of catalysts, the polymerization time and the polymerization temperature on the inherent viscosity were studied; also the water absorption and weight loss rate with PLA and PLA-co-Asp were investigated. Under the condition of160℃for8h, the mass ratio between LA and MMD is90:10, the mount of catalysts is0.3%, the inherent viscosity is the best, the copolymer has superior water absorption and weight loss rate.Finally,a novel biodegradable starch grafted copolymer, starch-g-poly(lactide)(st-g-PLA),was synthesized in situ by the ring-opening graft polymerization of a lactide monomer onto the surface of the SM-ST granules.the structure was characterized with IR,XRD.Under the condition that the mass ratio between SM-ST and lactide is1:3,the time is24h,the mount of catalysts is1.5%,the grafted efficiency is the best.And the property of starch grafted copolymer as controlled release film was researched,the conclusion was achieved:the urea packed with starch grafted copolymer,the release time was longer;the longer grafted efficiency, the better the controlled release effect.