Investigating Temperature-Dependent Microscopic Deformation in Tough and Self-healing Hydrogel Using Time-Resolved USAXS.

Tough and self-healing hydrogels are typically sensitive to loading rates or temperatures due to the dynamic nature of non-covalent bonds. Understanding the structure evolution under varying loading conditions can provide valuable insights for developing new tough soft materials. In this study, polyampholyte hydrogel with a hierarchical structure is used as a model system. The evolution of the microscopic structure during loading is investigated under varied loading temperatures. By combining ultra-small angle X-ray scattering and Mooney-Rivlin analysis, it is elucidated that the deformation of bicontinuous hard/soft phase networks is closely correlated with the relaxation dynamics or strength of non-covalent bonds. At high loading temperatures, the gel is soft and ductile, and large affine deformation of the phase-separated networks is observed, correlated with the fast relaxation dynamics of non-covalent bonds. At low loading temperatures, the gel is stiff, and non-affine deformation occurs from the onset of loading due to the substantial breaking of non-covalent bonds and limited chain mobility as well as weak adaptation of phase deformation to external stretch. This work provides an in-depth understanding of the relationship between structure and performance of tough and self-healing hydrogels. This article is protected by copyright. All rights reserved.