纤维素纳米晶液晶自组装机制研究及其功能复合材料的构筑

Due to the combination of excellent physical properties and virtue of biomaterials, cellulose nanocrystals(CNC) isolated from renewable resources have attracted growing interest in a wide range of scientific and industrial fields. Among the many potential applications, the anisotropy CNC nanorods are notable for the striking ability to self-organize into chiral nematic (cholesteric) liquid crystal phase in concentrated solution．However, the structural origin of this phenomena has not been fully understood yet. In-depth study of CNC self-assembly mechanism and regulation methods will provide a theoretical basis for the development of composites with the self-assembled structure of CNC. In this project, we plan to regulate the crystal modifications of CNC and its liquid crystal self-assembled structure. By utilizing modern characterization techniques, the microstructure of single CNC nanorod and the self-assembled structure of CNC aggregates will be studied by Nano-IR and synchrotron radiation WAXD/SAXS techniques, respectively. By this way, the correlation of CNC crystal modifications and its liquid crystal self-assembly structure will be explored. Meanwhile, by establishing in situ monitor accessory, the formation mechanism of CNC self-assembly behavior under flow field will be also investigated. Based on the understanding of CNC self-assembly mechanism and mastering the structure controlling method, we will develop the cellulose-based materials with diverse advanced functionalities via vacuum-assisted self-assembly technique. Moreover, we will investigate the effect of coupling interaction of each component on the structure and properties of resultant composites.

从天然高分子纤维素中分离出的纤维素纳米晶，因其具有优异的物理机械性能和生物材料的特性，引起学术界和工业界越来越广泛的关注。在纤维素纳米晶诸多潜在的应用中，其浓溶液能自组装形成具有左旋手性的胆甾相液晶这一能力尤为引人注目，但是该现象的结构起源仍未明确。深入研究纤维素纳米晶液晶自组装机制和调控方法，将会对研发基于其自组装结构的复合材料提供理论依据。本项目中，我们拟调控纤维素纳米晶多晶型及其液晶自组装结构，并运用现代表征技术，如纳米级显微红外技术与同步辐射光源分别研究单根纤维素纳米晶及其自组装结构，阐明纤维素纳米晶晶型结构与其液晶自组装行为的关系。同时，通过搭建在线检测装置，研究流动场条件下纤维素纳米晶自组装过程的结构演变。在对纤维素自组装机制与调控手段充分理解的基础上，采用真空抽滤技术构筑基于其液晶自组装结构的多功能复合材料，并探讨所制备材料各组分的耦合作用对其结构及性能的影响关系。

从天然高分子纤维素中分离出的纤维素纳米晶，因其具有优异的物理机械性能和生物材料的特性，引起学术界和工业界越来越广泛的关注。在纤维素纳米晶诸多潜在的应用中，其浓溶液能自组装形成具有左旋手性的胆甾相液晶这一能力尤为引人注目。前期研究中，我们发现纤维素纳米晶液晶自组装可通过真空抽滤快速实现。与常用的挥发成膜方式相比，该方法有很多优势。但其形成机制一直令人费解。本项目，我们深入研究纤维素纳米晶液晶流动场下自组装机制，并基于该方法制备了基于纤维素纳米晶手性液晶的功能复合材料。取得的主要成果有三方面： 1）揭示了纤维素纳米晶在真空抽滤流动场下的自组装机制，研究发现纤维素纳米晶在滤膜界面经过浓度富集、类晶体形成、取向增长及融合几个阶段，本质上属于一级相变过程。2）创新了羧基化的纤维素纳米晶制备方法，我们发现KMnO4在弱酸的温和反应条件下可高效制备羧基化的纤维素纳米晶，该方法比本领域研究者熟知并广泛采用的Tempo法有化学试剂用量少产量高的优势。并且，所得羧基化纳米晶良好的液晶自组装行为。3）发展了若干纤维素纳米晶真空抽滤彩色膜的改性方法，获得了同时增强增韧的纤维素纳米晶彩色膜。上述研究结果不仅丰富了纤维素纳米晶液晶自组装理论，也为其工业化应用提供了新技术。