基于坚果壳结构的高强韧木质纳米复合材料仿生设计

Synchronously reinforcing and toughening wood is a hot topic and great difficulty in wood modification. However, disruptive nanotechnology as a potential problem-solving approach is facing a bottleneck of controllable well dispersion of nanomaterials in matrix; and the corresponding academic system is lacking. Inspired from the microstructure of nut shell with high strength and toughness, the project proposes a novel technical hypothesis: generating nanomaterial-dotted polymer within wood cell lumen to reinforce and harden wood, and compression-densifying wood to constitute curved layered cell wall as toughening structure for impact energy absorption; and combining both the designs and the synergistic effect from the compatible multiple interfaces to create biomimetic wood-based nanocomposite with high strength and toughness which is similar to nut shell. Consequently, this study intends to design the polymer structure in terms of macromolecular theory, and to employ polyhedral oligomeric silsesquioxane (POSS) as aimed nanomaterial to match the functional group of the polymer. After the nano-POSS is dissolved into the functional monomers, the polymer precursor is impregnated into wood under pressure, followed by hot-compression treatment, and the aimed biomimetic product is finally derived. Furthermore, structural characterization and properties evaluation are combined to reveal the internal relationship between structure and performance of the material, and to analyze the bonding mechanism of the multiple interfaces, and accordingly to master the controllable rule of biomimetic structure design. Such a study could provide technological support for biomimetic design of novel wood-based functional materials, and scientific basis for enriching theories of wood reinforcement and corresponding appraisal systems.

同步增强与增韧木材是木材改性领域的热点与难点，而颠覆性纳米技术作为潜在解决手段却存在纳米材料可控均匀分散的瓶颈，相关理论体系也因之匮乏。受强韧坚果壳的微结构启发，本项目提出了新的技术构思：在木材细胞腔中原位生成纳米掺杂聚合物，起补强、增硬作用；通过压缩密实木材，使卷曲的层状细胞壁作吸收冲击能的增韧结构，并借助相容的多相复合界面协同作用，仿生构建类坚果壳的高强韧木质纳米复合材料。为此，本项目拟通过高分子理论设计聚合物结构，并选用多面体低聚倍半硅氧烷（POSS）为纳米材料以匹配聚合物功能基团，将其溶解于功能单体中后，加压浸注木材，最后经热压手段制得目标仿生材料。在此基础上，依据结构表征和性能评估，探明材料结构与性能间的内在关联，并解析多相复合机制，最终掌握仿生结构设计的调控规律，为仿生设计新型木质功能材料提供技术支撑，为丰富木材增强改性理论和相关评价体系提供科学依据。

本项目面向速生低质木材高性能改良领域，聚焦低质木材同步增强与增韧的关键技术瓶颈，受坚果壳强韧特性和关联的微结构启发，提出了“仿坚果壳结构的高强韧木材”的概念思想；并基于此，探索了有机-无机杂化纳米技术与木材压密技术的融合创新，确定了功能单体体系的优化配方和纳米多面体低聚倍半硅氧烷（POSS）的可控分散技术参数；初步构建了“主链为带有刚性酯基基团和柔性醚链结构的长链，侧链为纳米POSS聚集体，两者通过开环接枝形成立体交联网络结构”的聚合物结构设计规律；解析了木材强韧特性与微观结构的内在关联，初步探明了“木材强度同聚合物杂化结构、韧性同木材细胞壁卷曲结构的关联占主导地位；木材、聚合物和纳米POSS三相界面融合辅助提高强度和耐久性”的仿生结构设计调控规律，这将为丰富木材增强韧改性理论和仿生设计新型木质功能材料提供科学依据和技术支撑。