【作者】 李志勇；

【导师】 沈贤德；

【作者基本信息】 哈尔滨工程大学 ， 应用化学， 2009， 硕士

【摘要】 聚乳酸(PLA)是一种重要的生物可降解高分子材料,具有良好的降解性、生物相容性和较好的力学性能,其不仅可以作为生物医学材料用作药物缓释载体、外科植入材料和组织工程支架材料,而且可作为通用塑料用于农业、包装材料、建材及服装等领域,应用前景良好,是近年来生物可降解高分子材料研究的热点。本文对聚乳酸的合成方法进行综述,比较了各种主要合成方法,最终认为熔融／固相缩聚法是合成聚乳酸的较有效的方法。着重研究了以二水合氯化亚锡(SnCl2-2H2O)和对甲基苯磺酸(TSA)为复合催化剂,熔融／固相缩聚法合成聚L-乳酸。分别考察了熔融缩聚阶段脱水预聚、催化剂配比及用量、反应时间、温度及体系真空度等条件的影响和固相聚合阶段聚合工艺对聚乳酸合成的影响。通过红外光谱(FT-IR)和核磁共振波谱(1H-NMR和13C-NMR)分析表征了聚乳酸的结构,凝胶渗透色谱(GPC)和乌氏粘度计相结合测定其分子量及分子量分布；通过差示扫描量热仪(DSC)、热失重分析仪(TG)测试聚乳酸的结晶性能、熔融行为和热分解行为,偏光显微镜(POM)对其结晶和熔融情况进行直观的观察；利用旋光仪表征分析各实验阶段的消旋行为。研究表明,SnCl2·2H2O/TSA复合催化剂对乳酸熔融缩聚有较好的催化效果。本体熔融缩聚法合成聚L-乳酸较为合适的工艺条件为：催化剂用量为0.5wt%,聚合温度180℃,真空度0.098MPa,反应时间为10h。此时聚乳酸的粘均分子量为6.17×104,分子量分布1.37,且产率较高,色泽较浅。以熔融缩聚粗产物为原料,固相聚合合成聚L-乳酸较为合适的工艺条件为：首先在105℃下等温结晶2h,然后设定温度145℃,真空度0.098MPa,聚合时间15h(变温控温方式更好),所得聚乳酸颜色没有加深,分子量为1.56×105,是固相聚合前的2.6倍。在以上研究的基础上,本文考察了聚乳酸的降解性能,发现聚L-乳酸具有良好的降解性能。同样条件下,不同分子量的聚乳酸降解速率不同,分子量高的降解相对较慢,分子量低的降解相对较快；聚乳酸在不同环境介质中的降解速率也不同,酸性介质中的降解比在中性介质中快,在0.01mol/L盐酸水溶液、去离子水、pH值7.4的磷酸盐缓冲溶液三种介质中,盐酸水溶液的降解速率最大。更多还原

【Abstract】 Poly (L-lactic acid) (PLLA) is one of the most important biodegradable polymer materials that have degradation ability, good biocompatibility and mechanical properties. Therefore, it has found wide applications not only in biomedical fields as drug delivery carriers, surgical implants and tissue engineering scaffolds, but also in industrial and agricultural fields as general plastics. Because of its bright prospects, PLLA has attracted much attention from both industrial and academic fields.In this study, first, synthetic approaches of PLLA have been summarized and reviewed, from which we arrive at a conclusion that melt/solid polycondensation is one of the most competitive method to synthesize PLLA. Then, based on this viewpoint, melt/solid polycondensation of PLLA catalyzed by the well-known SnCl2-2H2O/TSA catalyst system have been studied in detail. In order to optimize the technology parameters, the effect of catalyst ratio and amount, reaction time, temperature and system vacuum on the molecular weight and field of PLLA had been investigated both in melt polycondensation and solid polymerization. The structure of PLLA was analyzed by FT-IR and NMR, the molecular weight and distribution was tested by GPC and Ubbelohde viscometer, the crystallization, melting and heat decomposition behaviors of PLLA were studied by DSC and TG. And then, the method of POM was used to observe and identify the crystallization and melting process directly. At last, we made use of polarimeter to analyze the specific rotatory power of PLLA.The study indicated that, with SnCl2·2H2O/TSA as the catalyst, the comparatively appropriate reaction conditions of melt polycondensation are as follows:the catalyst amount is 0.5wt% to OLLA, polymerized at 180℃for 10h under a system vacuum of 0.098MPa. As a result, the maximum viscosity average molecular weight of PLLA is 6.17×104, with a narrow molecular-weight distribution, high production rate and light color. In regard to the solid polymerization, the more appropriate technology parameters are to keep temperature at 105℃for 2h, then polymerized at 145℃,0.098MPa for 15h. Finally the maximum viscosity average molecular weight of 15.6×104 is achieved, which is 2.6 times higher than that of PLLA prepared by melt polycondensation.Based on the study mentioned above, the degradation of PLA in different medium was discussed. It is reasonable to conclude that the degradation of high molecular weight PLLA is slower than that of low molecular weight, and that the degradation of PLLA in acid medium is faster than that in neutral medium. For the three medium:0.Olmol/L hydrochloric solution, de-ionized water and pH 7.4 phosphate buffer solution, PLLA degrades faster in 0.Olmol/L hydrochloric solution.更多还原