纤维素气凝胶各向异性交联-微结构协同设计机制及构效关系

The disordered porous structure of cellulose aerogels leads to the poor mechanical properties, including compressive strength and elastic modulus, which is the main problem to restrict the development of functionalization and industrialization. Therefore, it is significant to thoroughly analyze the structure-activity relationship of rigid structure construction and mechanics performance of the porous materials. This project intends to break through the poor strength and elasticity problem of wood cellulose nanofiber aerogel. The collaborative design of anisotropic three-dimensional (XY, YZ, XZ) ordering crosslinking structure and pyrolysis microstructure regulating enhances the aerogel mechanical properties. Based on the principles and methods of material science structure design, we use coupling reaction, double gradient freeze-casting technology and the high temperature pyrolysis to manufacture the enhanced aerogels with anisotropic three-dimensional network structure. The project will clarify the building mechanism of bidirectional gradient freeze-casting on orderly anisotropy skeleton structure, reveal the influence law of high temperature pyrolysis on gel microstructure production and alienation, construct the stress-strain model of aerogel with different structure including isotropy, anisotropy and pyrolysis regulation and expound the structure-activity relationship between mechanical properties. Ultimately, the project will manufacture one kind of wood CNF aerogel material with excellent mechanical properties. This study will provide the basic research reserves for biologic materials functionalization and circle applications.

纤维素气凝胶无序多孔结构导致其力学性能（抗压强度、弹性模量）不佳，是制约该材料功能化、产业化发展的主要问题。因此，深入解析多孔材料的刚性结构构建与力学性能之间的构效关系具有重要的研究意义。本项目拟突破木质纳米纤维素（Cellulose Nanofiber, CNF）气凝胶强度低、弹性差的问题，通过各向异性三维（XY、YZ、XZ）有序化交联结构设计协同热解微结构调控实现气凝胶的力学增强。基于材料学结构设计原理，采用偶联反应、双梯度冷冻技术和高温热解构筑具有各向异性三维有序交联结构的增强型气凝胶，阐明双向梯度冷冻对各向异性有序骨架结构的构筑机理；揭示高温热解对凝胶微结构生成及异化的影响规律；构建气凝胶各向结构及热解调控的应力-应变模型并明确多孔材料结构构建与力学性能之间的构效关系；最终制备具有优异力学性能的木质CNF气凝胶材料。该研究将为生物质材料的功能化、循环应用提供基础研究储备。

纤维素气凝胶无序多孔结构是导致其力学性能不佳的关键因素，因此，从多孔材料的结构构建与力学性能之间的构效关系出发，解析了化学结构构建、空间结构构建对于多孔气凝胶生物质材料的力学性能具有重要的研究意义。该研究以TEMPO氧化制备的纳米纤维素为原料，通过多种绿色化学反应实现了纤维素表面的化学网络交联结构；基于材料学结构设计原理，采用均相冷冻、单向冷冻和双向冷冻对比方式，结合系列形貌表征、理化分析，明确了梯度冷冻对于冰晶生长有序化控制的作用机理，揭示了交联各向异性有序结构构建与力学性能间的构效关系，明晰了各向结构调控对其多孔气凝胶弹性性能的增强效果，并通过3D打印技术构建的三维各向异性结构协同化学交联验证了本项目提出的结构有序化对弹性性能提升机理；该研究最终实现了纳米纤维素气凝胶力学强度提升达到155.9%，弹性形变恢复能力提升82.7%，弹性模量提升291.0%。该研究将为生物质材料在高性能的可压缩抗疲劳多孔材料应用方面提供基础研究储备。迄今，本项目在国内外学术期刊上发表论文6篇，其中SCI收录5篇，单篇最高影响因子14.588，EI收录1篇，申请发明专利3件。一篇论文获得第八届梁希青年论文奖三等奖。