Collaborative Research: Interfacial Self-healing of Nanocomposite Hydrogels

自修复聚合物是一种合成材料，能够在没有人工干预的情况下自主修复损伤。它们在各种工程应用中展示了可持续技术的巨大潜力，包括人造肌肉和皮肤、柔性电子产品、软机器人等。然而，自修复聚合物的最新设计仍然处于试错阶段，缺乏足够的理论指导。该奖项支持基础研究，以阐明纳米复合水凝胶的自我修复机制，该水凝胶由纳米颗粒交联的水介质聚合物网络组成。从这个项目中获得的知识将为自我修复聚合物提供机械方面的见解，这些聚合物能够在损坏后恢复其功能。这项研究不仅将促进自愈力学的基础科学研究，而且将通过进一步发展和提高以软材料为基础的可持续技术来促进国家的健康、繁荣和福祉。该项目还将在固体力学、聚合物科学、机械工程和下一代劳动力发展的高性能计算领域培训一批不同的学生。该项目的教育目标将通过课程开发、本科生研究机会、高中生暑期研究计划、K-12教师研究经验计划和K-12推广计划来实现。将作出特别努力，让代表人数不足的学生参与这一项目。尽管在自修复聚合物的合成和应用方面进行了广泛的研究，但构建自修复性能与材料/修复环境之间的机制关系仍然具有挑战性。关键的技术障碍是如何对聚合物网络在自愈过程中的微观结构演化进行物理模拟。该项目的中心假设是，纳米复合水凝胶的自愈强度取决于聚合物链在断裂界面上的扩散以及随后与纳米颗粒形成的交联物。为了验证这一假设，该项目将分子动力学模拟和分析理论相结合，研究了高分子链在自愈过程中的微观扩散反应行为和自愈后的宏观界面强度。计算和理论预测将通过由几种材料组成的纳米复合水凝胶的实验研究来系统地验证，这些水凝胶由几种材料组成，如颗粒浓度、颗粒尺寸和含水率，并在各种外部愈合控制下，如温度和延迟时间。这一跨学科的努力将为定量了解自修复聚合物的多尺度机理和提供高性能自修复聚合物的基本设计原则开辟有希望的途径。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Self-healing polymers are synthetic materials capable of autonomously repairing damages without human intervention. They have shown great potentials for sustainable technologies in diverse engineering applications, including artificial muscles and skins, flexible electronics, soft robotics and many others. Nevertheless, the state-of-the-art design of self-healing polymers remains at the trial-and-error stage with insufficient theoretical guidance. This award supports fundamental research to elucidate the self-healing mechanics of nanocomposite hydrogels that consist of water-mediated polymer networks crosslinked by nanoparticles. The knowledge obtained from this project will provide mechanistic insights into self-healing polymers that are able to restore their functionality after damage. The research will not only promote the fundamental science of self-healing mechanics, but also advance the national health, prosperity, and welfare through further development and enhancement of soft-materials based sustainable technologies. This project will also train a diverse group of students in the areas of solid mechanics, polymer science, mechanical engineering, and high-performance computing for next-generation workforce development. The educational objectives of the project will be realized through curriculum development, undergraduate research opportunities, summer research program for high school students, research experience for K-12 teachers program, and K-12 outreach program. Special efforts will be made to involve underrepresented students in this project. Despite extensive studies in the syntheses and applications of self-healing polymers, constructing the mechanistic relationship between self-healing properties and material/healing settings remains challenging. The key technical barrier is how to physically model the microstructure evolution of the polymer networks during the self-healing process. The central hypothesis of this project is that the self-healing strength of nanocomposite hydrogel is governed by the diffusion of polymer chains across the fractured interface and subsequent crosslinks formed with nanoparticles. To test this hypothesis, the project integrates molecular dynamics simulations and analytical theories to study microscopic diffusion-reaction behaviors of polymer chains during self-healing process and macroscopic interfacial strengths after self-healing. The computational and theoretical predictions will be systematically validated with experimental studies of nanocomposite hydrogels composed of several material compositions, such as particle concentration, particle size, and water fraction, and under various external healing controls, such as temperature and delaying time. The interdisciplinary effort will open promising avenues for quantitatively understanding the multiscale mechanics of self-healing polymers and providing fundamental design principles of high-performance self-healing polymers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.