【摘要】 辛酸亚锡催化下开环聚合制备聚乳酸(DL-PLA)-聚乙二醇(PEG)-聚乳酸三嵌段共聚物。用GPC、DSC、1 H-NMR、质量损失、静态接触角等方法在pH=7.4磷酸盐缓冲液中,37℃下研究了分子量Mn=400、1000和4000的PEG改性DL-PLA的降解行为。结果表明,PEG嵌段增强了共聚物的亲水性,降低了共聚物Tg,加速了共聚物降解,随着PEG分子量增加及两端DL-PLA链段增长,共聚物分子量下降速率加快。由研究结果得出,共聚物降解期间DL-PLA链段中的酯键随机断裂,PEG两端DL-PLA链段逐渐变短;降解后期DL-PLA链段进一步变短,并有短链DL-PLA均聚物产生,当PEG两端DL-PLA链段足够短时,共聚物在介质中溶解。更多还原

【Abstract】 Poly(DL-lactide)(DL-PLA)-polyethylene glycol(PEG)-poly(DL-lactide) triblock copolymers were synthesized by ring opening polymerization using stannous octoate as catalyst.The degradation behavior of triblock copolymers of DL-PLA modified by PEG with molecular weight of Mn=400,1000,and 2000 were investigated by GPC,DSC,1H-NMR,weight loss and static water contact angle test in a pH=7.4 phosphate buffer solution at 37℃.The results showed that introduction of PEG blocks increased the hydrophilicity of the copolymers and decreased their glass transition temperature,thus accelerated the degradation of the copolymers.The reducing of molecular weight of the triblock copolymers was increased with the increase of molecular weight of PEG and the length of DL-PLA blocks.According to the results,it was proposed that the ester bond cleavage proceeded at random along DL-PLA blocks and the length of DL-PLA blocks linking to PEG decreased gradually during the degradation.At the later stages of degradation,the length of DL-PLA blocks attached to PEG became shorter and shorter,meanwhile,the short chains of DL-PLA homopolymers were generated in the system.However,as the length of DL-PLA blocks became shorter enough,the triblock copolymers dissolved in the medium.更多还原