聚乳酸立构复合物规整度对其降解性能的影响

Research on Degradation Performance of Polylactide Stereocomplexation with Different Chain Stereo-regularity

通过开环聚合法,利用D,L-丙交酯合成不同规整度(XD)的左旋聚乳酸PLLA和右旋聚乳酸PDLA。用溶液浇铸法制得不同规整度的聚乳酸立构复合物SC-PLA,并在50℃缓冲溶液中进行降解。通过分析剩余质量、溶液pH值、热性能(DSC)、表面形貌(SEM)、电离子喷雾质谱(ESI-MS)等评价SC-PLA的降解性能。结果表明:相同规整度时,SC-PLA降解速率小于PLLA,但pH值变化大于PLLA,立构复合物SC的存在使材料比常见PLLA更耐水解;立构规整度下降会使SC-PLA的结晶度降低,材料的降解速率加快;降解使材料的结晶度上升,立构复合物晶体SC与均聚物晶体HC熔点降低;高规整度SC-PLA相对于相同规整度PLLA及低规整度SC-PLA,其降解产物分子链长度更短。

PDLA and PLLA with various chain stereo-regularity （XD） were obtained through ring-opening po- lymerization. PDLA and PLLA with similar XD were blended with 1 ： 1 weight ratio and then films were obtained through solution cast. They were subjected to hydrolytic degradation in buffer solution at 50 ℃, and the degradation processes were monitored by following mass loss, pH of the aging medium, thermal properties, surface changes,and degradation product patterns analysis. The results show that SC-PLA is more stable during aging process compared with common PLLA which has the same stereo-regularity. The decrease of stereo-regularity of SC-PLA leads to the decrease of crystallinity and accelerates the degradation process. The melting temperatures of both homocrystallites and stereo-complex crystallites of these samples shift to lower temperature while the crystallinity increases with the time. Hydrolysis of SC-PLA （XD = 100%） results in shorter but more acidic degradation products, compared to PLLA with the same XD and SC-PLAs with a lower XD.