氯化钙/甲酸溶解体系下氯化钙质量分数对蚕丝溶解性的影响

Effect of CaCl_2 concentration on solubility of silk in CaCl_2-formid acid system

采用氯化钙/甲酸(CaCl2/FA)溶解体系对丝素进行溶解,讨论不同CaCl2质量分数对丝素溶解性的影响,通过流变、SEM、红外光谱以及X衍射等测试手段表征丝素溶液及其干燥膜的结构特征。结果表明:在相同温度、溶解时间条件下,丝素的溶解度随着CaCl2质量分数的增加而增加,溶解呈现先快后缓的上升趋势;当CaCl2质量分数为2%、5%、8%、10%时,丝素溶液的流变曲线中剪切黏度随剪切速率的增大先增加后减小,CaCl2质量分数为1%时,黏度明显高于其他质量分数值溶解下的丝素溶液。通过SEM可清晰地观察到丝素溶液以及丝素干燥膜中的纳米纤维结构。红外光谱分析表明,该溶解体系制备的丝素蛋白大分子以β-折叠结构为主,而CaCl2质量浓度的不同对丝素的结构影响不明显。X衍射分析表明,丝素在9.5°、20.5°和23.9°处出现结晶峰,均属于Silk II结构。

CaCl2/formid acid （FA） system was adopted to dissolve silk fibroin,the effect of different CaCl2 concentrations on the solubility of silk fibroin was discussed.Rheological behavior,and SEM,FTIR and XRD analyses were applied to characterize the silk fibroin solutions and dried films thereof.The results indicated that the solubility of silk fibroin was increased with the increase of the concentration of CaCl2 at the same dissolution temperature and time,and the speed of dissolution was higher at first than afterwards.The shear viscosity was increased first and then decreased in the rheological curve when the concentration of CaCl2 was 2%,5%,8% and 10%,respectively,and the viscosity when the CaCl2 concentration is 1% was remarkably higher than that of silk fibroin solutions dissolved at other concentrations.SEM results showed that nanofiber structures could be clearly observed in the silk fibroin solution and the silk fibroin dried.The results of FT-IR analysis showed that silk fibroin macromolecules prepared by the dissolution system mainly was 3-folded structure,and the concentration difference of CaCl2 had no obvious influence on the silk fibroin structure.The XRD diffraction analysis showed that silk fibroin had crystal peaks at at 9.5°,20.5° and 23.9°,which all belonged to the Silk Ⅱ structure.