The Study On The Synthesis And Performance Of Degradable Cross-Linked Polyurethane

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.