摘要 聚氨酯材料具备优良的组织相容性和血液相容性，优异的机械性能，可通过浇注、混炼等方法加工成型，并且价格低廉。但由于传统聚氨酯材料不可降解，限制了其在医学领域应用。采用可完全生物降解的聚合物作为多元醇组分，与二异氰酸酯反应合成可降解聚氨酯，这类聚氨酯特别适合用于医学领域。可完全降解聚合物中的聚乳酸是以可循环植物资源为原料经由生物发酵或人工合成得到生物可降解的热塑性聚酯，其无毒、无刺激性，良好生物相容性、可生物分解吸收、强度高的特点，使其成为常用医用材料。 本文首先以4,4'-二苯基甲烷二异氰酸酯（MDI）或MDI与六亚甲基二异氰酸酯（HDI）混合物作为硬段，聚四氢呋喃醚二醇（PTMG）作为软段，3,3'-二氯-4,4'-二氨基二苯基甲烷（MOCA）作为扩链剂合成聚氨酯医用弹性体材料。采用红外光谱进行表征，结构符合预期。探讨了不同MDI用量，扩链剂用量及MDI与HDI二者并用对聚氨酯医用弹性体材料拉伸性能、撕裂性能和硬度的影响，较优的配方为：异氰酸酯与醇摩尔比例为3:1，扩链剂的用量为3.7%，HDI与MDI并用作为异氰酸酯组分比HDI或MDI单独使用各方面性能均有所提高。经MTT法细胞毒性测试，所合成聚氨酯弹性体浸提液毒性为l级，符合第Ⅲ类医用材料的细胞毒性要求。 对乳酸除杂，探讨乳酸除杂温度、除杂时间对乳酸含量的影响，除杂温度为90℃，除杂时间为40min时，乳酸含量达到最大值，为98.93%。以乳酸除杂产物熔融缩聚合成聚乳酸，通过红外光谱及核磁1H-NMR，证明制得了乙二醇作封端剂的羟基封端聚乳酸（PLA-OH）。并采用GPC分析了不同合成温度下羟基封端聚乳酸，合成温度为低温130℃，高温160℃时，合成的PLA-OH分子量大小适宜，分子量分布较窄。 将自制PLA-OH与PTMG作为混合多元醇组分与六亚甲基二异氰酸酯（HDI）反应，后再加入催化剂及扩链剂等合成可降解聚氨酯弹性体（PLA-PU），以红外光谱表征结构，符合预期。并对合成出的可降解聚氨酯弹性进行了力学性能、热稳定性、可降解性分析。PLA-OH含量为20%时，合成的可降解聚氨酯硬度适宜，拉伸性能、抗撕裂性能适于作为医用材料。TGA测试表明PLA-OH含量越大，可降解聚氨酯弹性体热稳定性越差，材料的可分解性能越好。在80℃水中和PBS缓冲液中降解，PLA-OH含量越大，材料降解性越好。加入PLA-OH后合成的聚氨酯具有了明显可降解性。

ABSTRACT Polyurethane material had excellent histocompatibility,hemocompatibility,and exceedingly good mechanical properties,which could be molded by pouring,mixing and other methods,additionally it was always under low prices.However,due to the traditional polyurethane material was non-degradable,its application limited in the medical field. Biodegradable polyurethane was synthesized by fully biodegradable polymer as the polyol component and diisocyanate,these polyurethanes were particularly suitable for the medical field.Polylactic acid was one of the fully degradable polymers,which was based on recyclable plant resources as raw materials,and it was a kind of biodegradable thermoplastic polyester could be obtained via biological fermentation or synthetic.Its characteristics of non-toxic,non-irritating,good biocompatibility,biodegradable,absorbable and high strength,which made it common medical material. Firstly,4,4'-diphenyl methane diisocyanate(MDI) or MDI/HDI mixture was used as hard segment,Polytetra methylene ether glycol(PTMG) was used as soft segment, 4,4'-methylenebis(2-chloroaniline)(MOCA) was used as chain extender,the raw materials above all was used to synthesize polyurethane medical elastomeric material. FTIR spectra characterized the structure，the result showed that the structure was in line with expectation.The influence of different MDI dosage,the amount of chain extender and MDI/HDI mixture on tensile strength properties,tear strength and hardness of medical polyurethane elastomer material were discussed and the result showed that the optimum formula was:isocyanate and polyol molar ratio of 3:1,chainextender in an amount of 3.7%.Compared to the HDI or MDI used alone,when HDI/MDI mixture was used as the isocyanate component,all aspects of performance were improved. MTT assay testing Cytotoxicity proved that toxicity of polyurethane elastomer extract liquor of all kinds were level l.The result corresponded to the cytotoxicity requirements of Class Ⅲmedical materials. Lactic acid impurity was removed,and discussed the effects of lactic acid impurity removal temperature and time on content of lactic acid.When impurity removal temperature was 90℃,impurity removal time was 40min,the lactic acid content reached the maximum 98.93%.Purified lactic acid was used to synthesize polylactic acid by melt polycondensation. FTIR and 1H-NMR proved that hydroxyl-terminated polylactic acid was prepared and ethylene glycol used as blocking agent.Analyzed hydroxy-terminated polylactic acid synthesized at different temperatures by GPC.The result showed that when low synthesis temperature was 130℃ and high synthesis temperature was 160℃,the PLA-OH molecular weight was suitable molecular weight distribution was narrow. The self-made hydroxy-terminated polylactic acid (PLA-OH) and polytetra methylene ether glycol(PTMG) as mixed polyol component and hexamethylene diisocyanate (HDI) reacted to make prepolymer,and then added the catalyst and chain extender synthesized biodegradable polyurethane elastomer (PLA-PU).FTIR spectra characterized the structure，the result showed that the structure was in line with expectation.The mechanical properties,thermal stability,biodegradability of biodegradable polyurethane elastomer was analyzed.When the content of hydroxy-terminated polylactic acid (PLA-OH) was 20%,the degradable polyurethanes had appropriate hardness,tensile properties,tear resistance,which was suitable as medical material.TGA test showed that the larger PLA-OH content, made worse biodegradable polyurethane elastomer thermal stability and better biodegradable properties.Degradation result in 80℃ water and PBS buffer solution showed that the larger PLA-OH content made better degradation property.In conclusion,after adding PLA-OH,polyurethane had obvious biodegradablity.