弹性木材强韧化可控构筑及界面结合机理研究

Improving the structure and assembling the function of wood chemical component, microfibril and hydrogen bonding, the elastic wood with high strength and high ductility could be developed, based on the wood cell wall characteristics. However, the strengthening and toughening mechanism of the elastic wood interface which regulated by the multi-scale wood structure is still unclear. To solve this key scientific question, this project will proceed as following: the wood cellulose microfibril skeleton (wood skeleton) will be prepared by the delignification treatments of wood. Afterwards, by modifying the structure and surface properties of the microfibrils, the elastic wood will be developed with the integration of polydimethylsiloxane (PDMS) elastomer into the wood skeleton. The orientation and structure responses of microfibrils under loading, and the stress transferring-blocking rules between the microfibrils and PDMS interface during the deformation will be explored, respectively. As a result, the synergistic effect of axial extension and contraction of microfibrils, and the interfacial cooperative behavior with PDMS, which reinforced the elastic wood will be clarified. Finally, the strengthening and toughening mechanism for the elastic wood will be investigated at wood cell wall level, and the interfacial bonding mechanism between microfibrils and PDMS will be found out as well. The achievements of this project not only can improve the basic theory of high-value utilization of wood resources, but also can support the elastic wood applications in the field of elastic substrate of biomass flexible wearable devices.

参照木材细胞壁结构特征，对其组分、微纤丝及分子间氢键进行多尺度的空间设计和功能化组装，有望实现兼具高强度与高延展性弹性木材的可控构筑。然而，木材的多尺度微纳结构对弹性木材界面的强韧化作用机理尚不明确。本项目拟对木材进行脱木质素处理获得木材天然纤维骨架；通过调控木材细胞壁微纤丝结构与表面性质，以木材天然纤维骨架为自支撑体复合聚二甲基硅氧烷（PDMS），可控构筑木材天然纤维骨架/PDMS弹性木材；研究木材细胞壁纤维素分子链间氢键的断裂与重组对微纤丝取向及结构变化的影响，探索形变过程中微纤丝与PDMS间界面应力的传递与阻断规律，解明微纤丝轴向伸缩及与PDMS间的界面协同行为对弹性木材强度与延展性的增效机制，在细胞壁水平阐明弹性木材强韧一体化作用机制及界面结合机理。项目研究成果可丰富木材高值化利用基础理论，对拓展弹性木材在生物质柔性可穿戴器件弹性基材领域的研究与应用提供理论依据与技术支持。

本项目从“木材纤维骨架增强弹性聚合物”结构-功能一体化的基础理论出发：（1）以轻木为原料，参照木材细胞壁化学组分与结构特征，通过脱木质素提取木材纤维骨架，并对其进行碱处理；研究碱处理条件下，木材纤维骨架孔隙分布、细胞壁微纤丝角及纤维素结晶结构的变化，探索微纤丝卷曲变形对纤维素分子间氢键相互作用的响应规律，阐明了碱处理过程中木材纤维骨架轴向形变行为的发生机制。（2）以上述木材纤维骨架为自支撑模板，在其纤维孔隙结构中引入弹性聚合物（聚丙烯酰胺或聚二甲基硅氧烷），研究纤维素与弹性聚合物分子间键合方式对复合体系内各组分分布、含量及微结构等的影响，建立了“木材纤维骨架/弹性聚合物”弹性木材的可控组装体系；并进一步采用了一种紫外光引发接枝聚合技术，增强木材纤维骨架与弹性聚合物间的界面结合性，制备获得了一种拉伸强度达30.76MPa，断裂伸长率约16.07%的弹性木材。（3）研究不同载荷（拉伸、压缩）作用下，弹性木材沿不同方向伸展与收缩行为的变化，分析形变过程中微纤丝与弹性聚合物间界面应力的传递与阻断规律，揭示了木材纤维骨架轴向延展性对弹性木材弹性形变的增效机制，并在细胞壁水平阐明了弹性木材强韧化界面结合机理。（4）在上述研究基础上，仿照“人造皮肤”将上述弹性木材与导电离子液相结合，并组装构建柔性传感器，探究其对不同外界刺激信号的智能响应能力；结果表明，这种导电弹性木材在反复形变过程中仍能保持较好的力学性能与稳定的电子传输效率，有望作为弹性基材应用于柔性传感器、软体机器人和可穿戴电子设备等领域。综上，本项目研究成果对丰富木材资源的高值化利用基础理论具有重要意义，为弹性木材结构-性能的多尺度优化设计策略在柔性电子器件弹性基材领域的研究与应用提供理论依据和技术指导。