摘要
聚氨酯(PU)具有优异的物理机械性能和良好的生物相容性及可降解性,已广泛用于制造各种医用器械,并在许多人工器官和外科材料中发挥着重要作用。本文主要合成了两个系列的交联聚氨酯类聚合物,并表征确认了它们的结
构,研究了它们的热性能和降解性能。
1)以乙二胺、氯乙醇和环氧氯丙烷为原料,经开环聚合反应制得链状聚醚胺PEA,然后再用不同的二异氰酸酯作交联剂交联,合成了4种体型交联聚合物;
2)通过丙烯酰氯和双官能团单体乙二胺反应引入不饱和双键,得到含有氨基的烯烃类聚合物单体N-(2-氨基乙基)-丙烯酰胺,然后通过自由基聚合得到含有活泼氨基的线型高分子聚合物聚N-(2-氨基乙基)-丙烯酰胺,再用不同的二异氰酸酯作交联剂交联,合成了3种体型交联聚合物。
对合成聚合物的结构采用红外光谱、核磁共振波谱进行了表征确认;用扫描电子显微镜(SEM)观察高分子聚合物的形态特征,用热重分析(TGA),示差量热扫描分析(DSC)等研究聚合物的热学性质,并对聚合物的生物降解性和光降解性进行了初步研究。
实验结果表明:
1)所制备的交联型聚氨酯具有良好的热稳定性。采用相同二异氰酸酯交联得到的交联聚合物,最大热分解峰值温度随交联剂含量的增加而升高,而聚合物的玻璃化转变温度随着交联剂含量的增加而逐渐降低。
2)交联剂种类和用量相同的条件下,聚醚胺类交联聚合物的热稳定性大于聚丙烯酰胺类交联聚合物的热稳定性。
3)当线型预聚体(聚醚胺或聚丙烯酰胺)和交联剂用量相同时,采用苯环类交联剂得到的交联聚合物的热稳定性高于使用烷烃或环烷烃类交联剂得到的聚合物。
4)所合成的交联聚合物经过光降解以后,其热分解峰值温度有所降低,热失重百分比有所增大,玻璃化转变温度有所降低,降解后聚合物的表面都出现了明显的孔洞。
5)聚醚胺(PEA)基聚合物的生物降解实验结果表明:在无水解酶的溶液中,聚合物重量损耗远远小于在有酶的溶液中聚合物的重量损耗;随着交联剂用量的增加,聚合物的降解速率逐渐降低;随着酶浓度的增加,聚合物的降解速率逐渐增加。
本文合成的两类聚氨酯含有羟基或氨基官能团,利用这些官能团可以继续与其它活泼单体反应,从而可以根据需要改变高分子聚合物的特性,通过对它们进行改性还可以进一步拓展这些聚合物的应用领域。作为可降解功能高分子材料,这些聚合物将会满足不同需要而有潜在的应用前景。
Polyurethanes (PU) are widely used to manufacture various medical apparatus, and play an important role in the artificial organs and surgical materials, because of their outstanding mechanic performance, excellent biocompatibility and degradability. In this study, two series of cross-linked polyurethanes were synthesized and characterized in structure, and their thermal-stability and degradability were studied as well.
1) A chain-shaped poly (ether-amine) (PEA) was synthesized through cycle-opening polymerization, using ethylene diamine, 2-chloroethanol and epoxy chloropropane as raw materials. PEA was then cross-linked with different diisocyanates to produce four cross-linked space polymers.
2) chain-shaped polymer poly [N-(2-aminoethyl)-acrylamide] was synthesized through free-radical polymerization using acryl chloride and ethylene diamine as raw materials. Poly [N-(2-aminoethyl)-acrylamide] was then cross-linked with different diisocyanates to form three space polymers.
The structures of the synthesized polymers were characterized and confirmed with IR spectra and NMR spectra (1H NMR or 13C NMR). Scanning Electron Microscope (SEM) was employed to observe the surface morphology of the polymers. The thermal performance was examined using Thermogravimetry Analysis (TGA) and Differential Scanning Calorimetry (DSC). The biodegradability and photo-degradability of the polymers were primarily investigated as well.
It was found that:
1) The synthesized cross-linked polyurethanes all possessed good thermo-stability. When the same diisocyanate was used as cross-linking agent, the decomposition peak temperature increased along with the content of the diisocyanate while the glass-transition temperature decreased.
2) When the same quantity of same cross-linking agent was employed, the thermal-stability of the cross-linked poly (ether-amine) excelled those of cross-linked polyacrylamide.
3) When the quantity of linear preformed polymer [the poly (ether-amine) or polyacrylamide] was equal to that of diisocyanate, the thermal stabilities of the cross-linked polymers from the diisocyanate containing phenylenes were higher than those of polymers from the diisocyanate containing alkylenes or naphthenes.
4) After the photo-degradation of the synthesized cross-linked polymers, in their thermal-analysis, the thermal-decomposition peak temperatures decreased, the thermal weight-loss percentage increased, and the glass-transition temperature lowered; in addition, apparent holes or cracks appeared on the surface of the polymer.
5) It is shown in the biodegradation of the poly(ether-amine)-based polymers that, in the absence of the hydrolysis enzyme, the weight-losing rates of the polymers were far lower than those in the presence of the enzyme. The degradation rate decreased when the quantity of the cross-linking agent increased, but increased along with the concentration of the enzyme.
The two series of polyurethane synthesized in this study contains hydroxy or amino functions, which can react with other active monomers to modify the characteristics of the polymers, thus can broaden the application of the polymers. These polymers will fulfill different needs as degradable functionalized macromolecular materials, and promise a potential future.
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