采用氯化钙-甲酸溶解新方法,制备了氯化钙含量分别为1.50%(w,质量分数)和3.00%(w)的新型丝素蛋白膜SF-1.5和SF-3.0。运用傅里叶变换红外光谱技术和X射线衍射技术对样品的分子构象和结晶结构进行了表征。同时,利用热重技术对比研究了两种膜的热稳定性和热分解特性,依据Kissinger、Ozawa和Vyazovkin模型,考察了氯化钙含量对丝素蛋白膜热分解反应的热力学参数和动力学参数以及其机理函数的影响。结果表明,丝素蛋白膜SF-1.5中蛋白分子主要以β-折叠结构为主,丝素蛋白膜SF-3.0中蛋白分子构象主要以无规卷曲为主;SF-3.0膜在不同升温速率下的分解温度、活化能和活化焓均低于SF-1.5膜,SF-1.5膜的热稳定性优于SF-3.0膜。另外,利用Achar法和Coats-Redfern法研究发现:丝素蛋白膜在190.00-330.00°C的热分解过程遵循二维扩散(圆柱形对称)机理。
A new CaCl2-formic acid dissolution method was used to prepare silk fibroin (SF) films. Films SF- 1.5 and SF-3.0 were prepared using 1.50% (w, mass fraction) and 3.00% (w) CaCl2-formic acid solutions, respectively. The molecular conformations and crystal structures of the films were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The thermal stability, thermal decomposition properties, and effect of CaCl2 concentration on the thermodynamic parameters, kinetic parameters, and formation mechanism of the SF films were investigated using thermogravimetry techniques and the models of Kissinger, Ozawa, and Vyazovkin. The results showed that the SF-1.5 film mainly contained β-sheet Structure, While the main molecular conformation in the SF-3.0 film was random coils. The decomposition temperature, activation energy, and activation enthalpy of SF-3.0 were lower than those of SF-1.5, while the thermal stability of SF-1.5 was higher than that of SF-3.0. In addition, the thermal decomposition of the SF films was studied by the Achar and Coats-Redfern methods. The mechanism of decomposition of these SF films followed the two-dimensional diffusion (cylindrical symmetry) law in the temperature range of 190.00-330.00℃.