生物质纳米纤维宏观组装体的构筑及功能化研究

Although the nanoscience and nanotechnology have been well developed in the past two decades, it is still remain a challenge to achieve the controllable synthesis and chemical functionalization of nano-building blocks in large-scale and the desirable functionalities of macroscopic architectures. In this project, we propose a general concept of green and sustainable strategy for the synthesis of biomass-based nanofibers and their macroscopic assemblies with high performance. By combining chemical pre-treatment and mechanical exfoliation, we will develop the synthetic routes for large-scale fabrication of cellulose and chitin nanofibers by starting with cheap biomass. Particularly, we will identify the key factors that determine the size, crystallinity, surface chemistry, dispersibility, and yield of cellulose and chitin nanofibers. Furthermore, a series of environment-friendly, cheap, and high-performance macroscopic assemblies of these biomass-based nanofibers will be designed and fabricated, including fibers, membranes for gas/liquid separation, ion exchange membranes for fuel cells, separator membranes for batteries, hydrogels/aerogels, and polymer composites. Different techniques will be involved for assembling of biomass nanofibers, such as surface chemical functionalization, solution processing, and microbial fermentation. Importantly, we will try to fundamentally understand the correlation between the structural parameters of nanofibers and the performance of their macroscopic assemblies, and thus providing general and significant information for designing next-generation high-performance macroscopic assemblies of nano-building blocks.

随着纳米结构材料研究的不断深入，纳米材料的宏量制备、结构表面或界面的功能化以及通过纳米基元组装实现不同功能的集成是解决纳米材料未来应用关键科学问题之一。本项目拟以绿色可持续制备技术理念为导向，以廉价生物质为原料，采用化学预处理和机械剥离相结合的策略，系统开发纤维素、几丁质等生物质基纳米纤维的宏量制备技术；探明影响纤维素和几丁质纳米纤维的尺寸、结晶性、表面化学功能、分散性、以及产率的制备参数；结合表面化学修饰、溶液相加工、生物发酵等技术手段，构建一系列环境友好、价格低廉、性能优异的生物质纳米纤维宏观组装体，主要包括：工程纤维、气/液相分离膜、燃料电池离子交换膜、锂离子电池隔膜、水凝胶和气凝胶、聚合物复合材料等；并拟将从基础上着重理解生物质纳米纤维的结构参数与组装体性能二者之间的内在关联机制，进而为下一代高性能纳米基元宏观组装体的构建奠定理论基础。

近年来，国内外在纳米基元宏观组装体的构筑和功能化研究方面取得了系列重要进展，要将具有独特性能的单个纳米颗粒组装成为实际功用性的宏观材料仍是一大挑战。本项目按照项目计划书开展系列研究工作，取得的研究成果主要包括：1）研制了基于价廉的细菌纤维素的一类新型纳米纤维固体酸催化剂材料。通过不完全碳化和磺化天然纳米纤维素，制备了碳基固体酸催化剂，该催化剂在一系列重要的酸催化反应中性能均优于目前通用的固体酸催化剂；2）发展了一种催化热解的方法来改变木质纳米纤维素的热解方法，制备出具有很高的电导率和比表面积高质量的超细碳纳米纤维气凝胶材料。该气凝胶材料作为自支撑超级电容器电极，表现出优异的电化学性能；3）发展了一种通用的生物合成方法——固态基底-气溶胶生物合成法，通过原位实时程序化沉积纳米单元气溶胶，实现了原位生长的纳米纤维素与不同纳米单元的均匀复合，制备了一系列纳米结构单元含量可控、形状规则的宏观尺度大块细菌纤维素纳米复合材料。说研制的碳纳米管/细菌纤维素复合材料薄膜的导电性与力学强度综合性能优于以往报道的所有同类材料；4）发展了一种使用系列磷酸盐调控细菌纤维素热解转化为碳纳米纤维气凝胶的热解方法，实现了碳纳米纤维气凝胶的宏量制备。该碳纤维气凝胶材料继承了细菌纤维素从宏观到微观的多级次结构，表现出优异的热机械稳定特性。