木质纳米纤维手性向列的诱导与固定及其光响应机理研究

Wood cellulose nanofiber is able to arrange in a chiral nematic order spontaneously under particular condition, which is considered as one of the promising responsive photonic intelligent materials due to its excellent selective light reflection and optical rotator properties. How to induce and fix such chiral nematic order in cellulose nanofiber is the fundamental issue for the application of wood cellulose nanofiber in these advanced intelligent materials. Whereas, micro-nano structure of nanofiber and its self-assembly influence significantly. In the present proposal, asymmetric flow field flow fractionation, coupled with multi-angle light scattering detection, was selected to separate wood cellulose nanofiber continuously and regulate its micro-nano structure. By analyzing interactive relationship among micro-nano structure, surface charges and electrolyte and their influence on the formation of chiral nematic order, we can build the induction mechanism of chiral nematic order of wood cellulose nanofiber. We would also perform the investigation of microtopography, fiber orientation and interfacial adhesion of cellulose nanofiber during self-assembly, with the intention to reveal the response relationship between controlled self-assembly and chiral nematic order. On this basis, we can establish the photon transmission and scattering mechanism of chiral nematic order under controlled self-assembly, and achieve the basic application theory of responsive photonic materials of wood cellulose nanofiber. These researches not only provide thoughts and methods for high-efficient utilization of wood cellulose nanofiber, but produce new theories and technical supports to accelerate the development of traditional biomass in novel and advanced materials field.

木质纳米纤维在特定条件下能自发形成手性向列排布，表现出优异的选择性光反射和旋光等光学特性，是一种良好的光响应智能材料。这种手性向列的形成与固定是木质纳米纤维在光响应材料应用中的基础与关键，而纤维的微纳结构及其自组装具有非常重要的影响。本项目提出采用非对称流场流-静态多角度光散射技术实现木质纳米纤维连续分离与微纳结构调控，解析木质纳米纤维的微纳结构、表面电荷、媒介电解质对其手性向列形成的交互关系，建立具有连续微纳结构的木质纳米纤维的手性向列诱导机制；研究木质纳米纤维在自组装过程的微观形貌、排列取向、界面结合特性，揭示纳米纤维自组装调控与其手性向列的响应关系；在此基础上建立木质纳米纤维手性结构诱导调控与其光子传导及散射机理，获得木质纳米纤维光响应材料的应用基础理论。这些研究不仅为推动木质纳米纤维高附加值利用提供思路和方法，也为传统生物质资源在新材料等领域的发展提供新的理论与技术支撑。

手性向列排布的木材纳米纤维具有选择性光反射、旋光等光学性能，在光信息储存与液晶显示等领域应用前景广阔，但纤维手性向列的形成固定和转移复制机理仍未完全揭示。本项目探明了硫酸浓度、水解时间、水解温度、均质次数、均质压力等工艺条件对木质纳米纤维表面电荷、微观结构等物化性质的影响规律，解析并发现了木质纳米纤维表面性与长径比共同影响其手性向列的形成与结构。综合分析了木材纳米纤维在自组装成膜时的溶液初始浓度、干燥温度、电解质含量、超声处理等因素对手性向列结构的影响规律，从流变学角度研究并揭示了木材纳米纤维物化特性对其胶体流变性能及其自组装迁移方式的作用机理。采用动态水分吸附仪对胶体水分蒸发速率进行了精细表征与数学模拟，首次发现纳米纤维胶体干燥速率快速跃升点，并推断该跃升点是纤维手性向列调控的分界点，即纳米纤维胶体浓度低于该分界点时向列排布仍可调控，而高于该分界点后向列结构基本固定、难以调控。设计出木材纳米纤维/铝酸锶荧光材料和木材纳米纤维/纳米银手性向列膜材料，研究了纤维结构与特性对复合材料微观形貌、组织结构、发光特性、旋光规律等的影响机制，发现手性向列薄膜的螺距大小随着纳米银粒子含量的改变而变化，且呈明显的二次曲线关系。这些发现为木材纳米纤维自组装成膜理论及其手性向列调控固定及其光学材料应用研究提供了重要支撑。.项目在《Journal of Materials Science》、《Scientific Reports》等发表论文7篇，其中SCI、EI收录论文5篇，申请/授权国家发明专利4件，获湖南省科技进步一等奖1项、梁希林业科学技术一等奖1项。培养硕士研究生1名，指导研究生获全国大学生小平科技创新团队1个，项目成员2人次由讲师晋升为副教授，项目负责人先后入选“国家青年人才托举工程”、湖南省湖湘青年英才等。参加第一届生物质能源与材料前沿青年论坛等6人次，做大会报告4人次，协助举办中国科协第319次青年科学家论坛、中国工程院“木材仿生光学工程前沿技术研究”学术研讨会。