Direct synthesis of poly(D,L-lactide-cholesterol) via melt copolycondensation and its characterization

Using D,L-lactic acid(D,L-LA) as the starting material and cheap SnCl_2 as the catalyst,poly(D,L-lactide-cholesterol) was directly synthesized via melt copolycondensation in place of the traditional ring-opening polymerization of lactide.The copolymer was systematically characterized by FT-IR,(()~1HNMR),DSC and GPC.The optimal synthetic conditions,including the feed molar ratio,the prepolymerization time and polymerization time,were discussed.When being catalyzed by 0.3% SnCl_2 at a feed molar ratio of cholesterol to lactic acid equating to 1∶66 and a reaction temperature of 140 ℃,the reaction mixture after prepolymerization for 4 h followed by polymerization for 10 h gave the target product with a yield of 85%.The weight-average molecular weight(Mw) of the copolymer was 3 600,which was higher compared to that achieved by the ring-opening polymerization of lactide.At the same time,the novel direct copolycondensation method was cheaper and more practicable than the traditional method of ring-opening polymerization of lactide.