蚕丝分级纳米原纤的可控溶解及其静电纺丝研究

Silk is a biological protein fiber with exceptional tunable mechanical properties such as high tensile strength and great extensibility, which originate from its hierarchical nanofibril structure. Nanofiber extraction directly from natural materials by physical or chemical methods is an important direction for constructing functional materials based on such nanofibers. Unfortunately, the present solvents for silk dissolution share a common feature of dissolution at the molecular level, which leads to the complete destruction of the silk hierarchical structure and noticeable degradation of the fibroin molecules. In this situation, the regenerated silk fibroin materials shows poor mechanical properties. Fortunately, Our recent work found a new solvent system for silk dissolution. The salt/formic acid blend solvent can dissolve silk at room temperature, more importantly, which characterized by preserving the natural nanofibrillar structure and removing the β-sheet crystal structure. In view of this, firstly, we will study the effect of salt/formic acid system parameters on the molecular structure, crystal structure and the fibril structure of silk during dissolution, such as type of the salt, salt concentration, formic acid concentration, temperature, time, elucidate the mechanism of silk dissolution in this solvent, and determine the key influence factors. Then optimum condition for controlling the nanofibril size and silk structure is also studied. Finally, electrospinning is employed to clarify the effect of nanofibril on the fiber formation, structure and property of electrospun nanofibers. The research will provide important reference data for the design and development of controlled structure and excellent performance of regenerated silk fibroin materials for application in high technoogy areas.

蚕丝具有优异的力学性能，这与其内部的多级纳米原纤结构关系密切。目前，通过物理或化学方法直接提取纳米原纤进行塑形已然成为天然高分子材料功能化再生的重要的热点课题。然而，已有的溶剂体系在重塑蚕丝的同时极大地破坏了蚕丝的原纤结构，甚至是分子结构，严重影响了再生丝素蛋白材料的性能。我们近期工作发现了盐-甲酸复合溶剂可以在常温常压分纤溶解蚕丝并破坏原纤内的结晶结构。鉴此，本课题拟首先深入研究盐种类、盐浓度、酸浓度、溶解温度与时间在破坏各级原纤间作用力及结晶区分子间作用力中的作用，确定影响蚕丝在纳米原纤尺寸溶解的关键因素，并分析溶解机理；然后研究盐-甲酸体系关键因素控制蚕丝溶解得到结构稳定、尺寸均一纳米原纤的条件；最后利用静电纺丝技术研究天然纳米原纤对再生丝素蛋白材料结构性能的影响，为今后基于天然纳米原纤构建结构可控与性能优异的再生丝素蛋白材料提供重要的理论参考与实验依据。

蚕丝具有优异的力学性能，这与其内部的多级纳米原纤结构关系密切。然而，目前尚无有效方法获得天然蚕丝纳米原纤结构，进而获得性能优异的的再生丝素蛋白材料。本项目针对该问题，开创性的采用低浓度中性盐/酸复合溶剂体系在常温快速高效溶解蚕丝，溶解同时保留蚕丝原有的原纤结构。由此得到的丝蛋白原纤溶液，可以被加工成致密膜、纳米纤维、多孔材料等再生丝素蛋白材料。研究同时发现脱胶工艺与盐浓度是影响纳米原纤尺寸的关键因素。本项目提出的低浓度无机盐复合酸溶解蚕丝新体系，不仅使得蚕丝的溶解更加简单高效，同时有利于再生丝蛋白材料的加工与应用，具有重要的应用价值。