受限空间中聚氨酯分子链的自调整及仿蜘蛛丝高韧纤维的构筑

Spider silk fibers having remarkable protein sequence structure contain nature's most outstanding mechanical properties and unrivalled elasticity along with biocompatibility and biodegradability, which are generally used for the fabrication of lightweight composites. However, owing to the difficulty in the large-scale cultivation of spiders, the application of spider silk fibers seems to be restricted. Therefore, the investigation of spider-like fiber becomes a research hotspot. In this research, polyurethane (PU) with the soft and hard segments was taken as the object, on the basis of molecular conformation for PU molecules, the effects of hard segment length and binary solvent system on the molecular conformation of PU molecules were investigated. The precise control of molecular chain microstructure for PU molecules and the preparation of microspheres structure for PU molecules in confined space were realized. Furthermore, the synergistic effect between microstructure modulation and macroscopic physical properties was elucidated. Most importantly, the spider-like fiber with high performance was fabricated. The mechanism for the effects of poor and good solvents in the phase transformation on the optimization of unmodified cellulose naonocrystals interface was revealed. The relationship between the mechanical properties and the surface hydrophilicity of high-performance spider-like fiber was established. The key fabrication technology of PU spider-like fiber was improved. The relationship between fiber mechanics, surface functionality, and microstructure was established.

蜘蛛丝因其优异的强度和韧性广泛地用于制造轻质高强的复合材料，但由于蜘蛛不能像蚕一样大规模地饲养，难以实现直接使用蜘蛛丝这一天然高分子材料，因此，仿蜘蛛丝纤维的研究成为仿生制备的热点。本项目以具有软硬段分离结构的聚氨酯为研究对象，从调控聚氨酯分子链的构象和聚氨酯与纤维素纳米晶须界面形态和结合力的角度出发，实现聚氨酯分子链微观结构的精准控制，阐明从微观结构调制到宏观物理性能强化的协同性，并构筑仿蜘蛛丝纤维。揭示不良溶剂/良溶剂混合溶剂在聚氨酯相转变过程中驱动形成的亚稳态体系对于聚氨酯与未改性纳米纤维素晶须界面的优化本质及机理，明确高韧仿蜘蛛丝纤维的力学性能、表面亲水性和透湿性能之间的平衡关系和影响因素。完善聚氨酯仿蜘蛛丝高韧纤维的加工成型过程及制备的关键技术，实现可控制备具有天然纤维表面性能的高韧仿蜘蛛丝纤维的可纺连续性与均一性，建立纤维力学、表面功能性与微结构的规律关系。

蜘蛛丝具有高强度、高弹性和高韧性，在纺织及军工领域中具有极大的应用前景，但是蜘蛛的互残生物特性极大阻碍了蜘蛛丝的大规模生产。因此，仿蜘蛛丝纤维的研究与开发成为仿生制备的热点和难点。本项目利用合成高聚物聚氨酯具有与蜘蛛丝相似的硬段-软段结构，基于高分子链在不同溶剂中构象的变化，通过良溶剂/不良溶剂对聚氨酯分子链进行调控。采用良溶剂/不良溶剂混合溶剂体系溶解聚氨酯预聚体，结合非溶剂致相转变原理和溶剂蒸发致相转变原理，制备了高韧的聚氨酯膜，系统地分析了膜的微观结构、宏观形貌和力学性能，阐明了从微观结构调制到宏观力学性能提升的机制。进一步地，采用微米级和纳米级纤维状及不规则形状的有机无机粒子，在聚氨酯硬-软结构的基础上构筑了硬段复合微区，实现了制备高填充比未改性粒子/聚氨酯复合材料的新方法。解析了受限空间中亚稳态体系驱动的聚氨酯分子链构象的调控优化聚氨酯与未改性填料粒子界面性能的机理，制备了高韧聚氨酯复合纤维。本项目发表论文10篇，申请中国发明专利12项，其中授权8项，参加国际学术会议4次，其中口头汇报1次，培养硕士研究生5人。本项目的研究结果突破了聚氨酯本体材料的力学极限，解决了聚氨酯与填料粒子的界面问题，为物理法构建高韧性的仿生纤维提供了新的解决途径。