4D气凝胶的多尺度结构对其力学性能及功能性的影响研究

Structural functionalization and functional diversification are the key difficulty during the intelligent materials develop process. Traditional aerogel has poor adaptability, which cannot adjust its own state according to environmental changes and meet the requirements of intelligent materials. Inspired by the structure of biological porous materials, we are looking for a new material (shape memory polymer) to develop a multi-scale structure smart aerogel by using pre-crosslinked ice template method. SMP shows large deformation and variable stiffness by various external environments stimulation. Through the reasonable structure optimization, modification and functionalization of material, this work achieves programmed control of its structure and functionality. The novel aerogel has three-dimensional multi-scale structure and can adjust its own state for adapting to environmental changes. In order to distinguish it from traditional aerogel, it is called four-dimensional (4D) aerogel. This study focuses on the evaluation of the structure, thermal, mechanical and driving properties of 4D aerogel and its composites, as well as the constitutive relationship between the influence of multi-scale structure on mechanical properties and functionality in order to reveal the influence mechanism of the structure on mechanical properties and stimuli-responsive behaviors. Based on the above research, 4D aerogel materials with multi-scale gradient structure are designed to construct active deformation structures and verify their underwater deformation behaviors. It provides valuable theoretical and experimental basis for its application in ocean development.

结构功能化及功能多样化是材料智能化发展中的关键难点。传统气凝胶自适应性差，无法根据环境变化调整自身结构，不满足材料智能化需求。受生物多孔材料结构的启发，本项目采用预交联冰晶模板法，独辟蹊径地引入形状记忆聚合物，利用其受环境刺激能够产生大变形和变刚度的特性，通过合理的材料结构优化、改性和功能化，研发具有多尺度结构的智能气凝胶，实现程序化控制其结构和功能性的目的。这种新型气凝胶不仅具有多尺度三维结构，还能够根据实际应用需求主动调整自身结构以适应环境变化，故区别于传统气凝胶将其称为4D气凝胶。本项目重点研究4D气凝胶及其复合材料体系的结构、热学、力学和驱动性能；分析多尺度结构与力学性能及功能性的本构关系，揭示结构对力学性能和激励响应特性的影响机制；基于以上研究设计具有多尺度梯度结构的4D气凝胶材料，构筑主动大变形结构，验证其水下变形行为，将为探索其在海洋开发中的应用提供有价值的理论和实验基础。

传统气凝胶自适应性差，无法根据环境变化调整自身结构，不满足材料智能化需求。气凝胶及其复合材料的智能化发展，将突破传统气凝胶的限制，本项目受生物多孔材料结构的启发，从气凝胶智能化设计及性能优化的角度出发，采用预交联和预编程策略，利用形状记忆聚合物受环境刺激能够产生大变形和变刚度的特性，通过合理的材料结构优化、改性和功能化，研制了具有多尺度结构的聚乙烯醇（PVA）基4D气凝胶及其复合材料，其水激励响应回复速度比多数无3D结构的水激励响应聚合物快2~3个数量级，且此过程中产生的吸力有利于提高传质通量、目标物与活性位点间的相互作用效率；采用理论力学方法对其进行分析，结合数值模拟对其进行优化；可控碳化对4D气凝胶结构与性能的影响；所研制的具有选择性吸附、检测或催化等能力的COF基功能材料，为4D气凝胶的多功能拓展奠定了基础；由功能化4D气凝胶和0.1 mol/L HCl/EtOH活化后的PVA/环氧（EP）构建的主动变形结构，为研制面向海洋资源利用的集吸附、催化或检测等多功能为一体的智能结构提供了理论支撑和实验依据。4D气凝胶及其复合材料将在国防建设、航天航空、海洋开发、污染治理、节能减排、绿色建筑、生物医药、柔性电子器件等领域有广阔的发展空间和应用前景。

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