丝素蛋白-粘土纳米复合材料的热力学及动力学行为研究

Research on the Thermal Stability and Relaxation Kinetics of Silk Fibroin-clay Nanocomposites

用常规DSC及TOPEM技术研究了丝素蛋白-粘土纳米复合材料的热力学及动力学行为,丝素链的松弛动力学可以用玻璃化转变过程中的有效活化能(E_a)及协同重排尺寸(V_g)来表征.与纯丝素蛋白相比,复合材料的玻璃化转变温度向高温移动,有效活化能显著提高,同时丝素蛋白-粘土的协同重排体积也有显著提高.有效活化能和协同重排尺寸的增加表明粘土片层的存在降低了丝素蛋白链的运动能力,从而提高了复合材料的物理和化学稳定性.

Standard differential scanning calorimetry （DSC） and multifrequence tempera- ture-modulated differential scanning calorimetry TOPEM has been used to study the thermal stability and relaxation kinetics of silk fibroin/clay nanocomposites. The relaxation has been characterized by determining the effective activation energy （Ea） and evaluating the sizes of cooperatively rearranging regions at the glass transition （Vg）. As compared to virgin silk fibroin, the clay nanocomposites shows the glass transition at higher temperature and demonstrates markly larger activation energy. The SF-clay system has also been found to have a significantly larger value of Vg, 3. 9 nm3 and 4. 7 nm^3 for SF-MMTN and SF-MMTA nanocomposites as compared to 3 nm^3 for SF. The increase in Ea and Vg reflects an increase in molecular cooperativity that is introduced by mutually dependent motion of the polymer chains anchored to the surface of clay sheets. The clay phase lowers the molecular mobility of SF which is another factor contributing to the increased thermal stability of the nanocomposites.