Dynamically crosslinked polymers and their composites have tremendous potential in the development of the next round of advanced materials for aerospace, sensing, and tribological applications. These materials have self-healing properties, or the ability to recover from scratches and cuts. Applied forces can have a significant impact on the mechanical properties of non-dynamic systems. However, the impacts of forces on the self-healing ability of dynamically bonded systems are still poorly understood. Here, we used a combined computational and experimental approach to study the impact of mechanical forces on the self-healing of a model dynamic covalent crosslinked polymer system. Surprisingly, the mechanical history of the materials has a distinct impact on the observed recovery of the mechanical properties after the material is damaged. Higher compressive forces and sustained forces lead to greater self-healing, indicating that mechanical forces can promote dynamic chemistry. The atomistic details provided in molecular dynamics simulations are used to understand the mechanism with both non-covalent and dynamic covalent linkage responses to the external loading. Finite element analysis is performed to bridge the gap between experiments and simulations and to further explore the underlying mechanisms. The self-healing behavior of the crosslinked polymers is explained using reaction rate theory, with the applied force proposed to lower the energy barrier to bond exchange. Overall, our study provides fundamental understanding of how and why the self-healing of cross-linked polymers is affected by a compressive force and the force application time.

中文翻译：

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利用机械力加速交联聚合物中的动态交换和自我修复

动态交联的聚合物及其复合材料在下一轮用于航空航天，传感和摩擦学应用的先进材料的开发中具有巨大的潜力。这些材料具有自我修复性能，或具有从划痕和割伤中恢复的能力。施加的力会对非动力系统的机械性能产生重大影响。但是，人们对力对动态结合系统的自我修复能力的影响的了解仍然很少。在这里，我们使用了计算和实验相结合的方法来研究机械力对模型动态共价交联聚合物体系自我修复的影响。令人惊讶地，材料的机械历史对材料损坏后观察到的机械性能恢复具有明显的影响。较高的压缩力和持续力会导致较大的自愈，表明机械力可以促进动态化学作用。分子动力学模拟中提供的原子细节用于理解对外部负载具有非共价和动态共价键响应的机理。进行有限元分析以弥合实验与仿真之间的鸿沟，并进一步探索其潜在机理。使用反应速率理论解释了交联聚合物的自我修复行为，并提出了施加的作用力来降低键交换的能垒。总的来说，我们的研究提供了对交联聚合物的自我修复如何以及为什么受压缩力和施力时间影响的基本理解。