Autonomous self-healing hydrogels: Recent development in fabrication strategies

Given the high demand for materials with long life, advancing the design of self-healable materials with multifunctional properties is of great importance. Such self-healing materials include gels which crucially involve dynamic bonds/interactions that can be broken but then subsequently reform as new bonds/interactions; the nature of these dynamic bonds determines the overall self-recovery performance of the hydrogels. Dynamic covalent and non-covalent bonds are widely applied to obtain self-healable hydrogels; thanks to their ability to rearrange and return to their original nature. This paper provides an overview of various mechanisms of dynamic bonds that have been used in self-healing gel fabrication methods, highlighting the impact of the nature of the bonds in the rearrangement process to heal the hydrogels. In this review, we concentrate on disulfide and diselenide exchange, host–guest, metal–ion, and hydrogen bonding interactions, presenting and discussing recent advances in this field. In closing, the issues and perspectives for obtaining self-repairable hydrogels are addressed.