【作者】 左文耀；

【导师】 冯亚凯；

【作者基本信息】 天津大学 ， 材料学， 2006， 硕士

【摘要】 随着新的治疗理念的层层不穷,目前迫切需要将可降解性和功能性结合起来,开发出新一代的可降解植入材料,而具有形状记忆效应的可降解材料正是这样一种很有应用前景的植入材料。本文合成了三种可降解的形状记忆聚氨酯材料,并对其在猪胰脂肪酶(PPL)溶液中的降解行为进行了研究。首先分别以乙醇酸和D,L-乳酸为原料合成出乙交酯和丙交酯,通过傅立叶红外光谱(FTIR)和氢核磁共振谱(~1H-NMR)的分析,表明所合成的丙交酯和乙交酯均具有较高的纯度;然后以乙交酯和丙交酯为原料、季戊四醇为引发剂、二丁基氧化锡为催化剂合成出数均分子量为10000、乙交酯含量为15 wt%的星形丙交酯/乙交酯共聚物,羟基滴定法和~1H-NMR的分析结果表明合成出的产物符合预期的设计要求,Mn为8800左右,乙交酯含量为15.4 wt%;最后在辛酸亚锡的催化下,丙交酯/乙交酯共聚物分别与和异佛尔酮二异氰酸酯(IPDI)、4,4’-亚甲基二苯基甲烷二异氰酸酯(MDI)和三甲基六亚甲基二异氰酸酯(TMDI)反应,合成出三种具有交联结构的聚氨酯材料-IPU、MPU和TPU,拉伸实验和循环热机械实验表明三种材料均具有较好的机械强度和形状记忆性能。通过考查材料在降解过程中重量、吸水率、溶胀度、凝胶含量以及机械性能的变化,研究了37℃下TPU材料在不同浓度PPL酶溶液中的降解行为,并利用ATR-FTIR分析了材料在降解过程中表面性质的变化,结果表明酶通过催化材料中酯键的断裂促进了材料的降解,且随着酶浓度的增加,材料的降解速率会逐渐增大,当达到一最大值后,材料的降解速率会逐渐下降。随后基于材料降解速率与酶浓度的关系研究了本体系的降解动力学,结果表明由于本降解体系的酶促反应是一个非均相反应,有别于建立米氏方程的均相酶反应,所以导致降解速率与酶浓度的关系与米氏方程发生了偏离,因此我们选择了一种非均相酶促反应动力方程对本降解体系进行了分析,并得到了满意的结果;最后根据对本降解体系的动力学分析,探讨了PPL酶在TPU降解过程中的作用机制:PPL酶对TPU材料的降解是通过两步来完成的,即PPL酶通过其结合区先吸附到材料的表面,然后在其催化区的作用下材料表面的分子链发生断裂,最终导致材料的降解,同时也解释了降解速率与酶浓度之间的关系,即高的酶浓度阻碍了酶催化区与材料表面高分子链的接触,无法催化酯键的水解,导致了降解速率的降低。更多还原

【Abstract】 With the growing number of novel therapeutic concepts, a new generation of biodegradable implant materials combining degradability with multifunctionalities is needed to be developed. The degradable polymers with shape-memory effect are considered to be potential candidates for the next generation of implant materials. In this thesis, three kinds of degradable polyurethanes with shape-memory effect were synthesized, and the enzymatic degradation behavior of these polymers was studied using lipase from porcine pancreas （PPL）.Firstly, glycolide and D,L-lactide were synthesized from glycolic acid and D,L-lactic acid, respectively. The high purity of glycolide and D,L-lactide was affirmed by fourier transform infrared （FTIR） spectrometry and proton nuclear magnetic resonance （¹H-NMR） spectrometry. Then, a star-shaped oligo[（D,L-lactide）-co-glycolide] with a number-average molecular weights （Mn） 10000 g·mol^-1 and glycolide content 15 wt% was synthesized from D,L-lactide and glycolide using pentaerythritol as initiator and dibutyltin oxide （DBTO） as catalyst. The synthesized oligomer was found to have Mn = 8800 g·mol^-1 and glycolide content of 15.4 wt% by means of hydroxy titration and ¹H-NMR, that reflected the structure of oligomer accorded with design specification. Lastly, three kinds of crosslinked polyesterurethanes, i.e. IPU, MPU and TPU, were synthesized by the coupling reaction of the oligomer in the presence of isophorone diisocyanate （IPDI）, 4,4-methylene di-p-phenyl diisocyanate （MDI） and trimethylhexamethylene diisocyanate （TMDI） as coupling agent, respectively. Tensile test and cyclic thermomechanical measurement showed the synthesized crosslinked materials had satisfactory mechanical strength and shape-memory property.The enzymatic degradation behavior of the polyurethane TPU was investigated in aqueous solution containing various PPL concentrations at 37℃by weight loss, water absorption, volumetric swelling degree, gel content and mechanical properties during the degradation of TPU film. ATR-FTIR was also used to investigate chemical structures of degraded TPU film. The result showed that the degradation of TPU film was accelerated via PPL catalyzing the hydrolysis of ester bond. The rate of enzymatic degradation increased to a maximum value with the concentration of PPL, followed by a gradual decrease. The kinetics of the enzymatic degradation was更多还原