Design and Applications of Dynamic Hydrogels Based on Reversible C═N Bonds

Abstract Dynamic hydrogels offer the opportunity to meet the expectations of smart materials with adaptable properties such as stimuli responsiveness, self‐healing, shear thinning, stress relaxation, dynamic viscoelasticity, energy dissipation mechanisms, time‐dependent adaptation, etc. In the past decades, reversible C═N bonds including imine, hydrazone, and oxime have received great research interest in the design of dynamic polymer networks (DPNs). Moreover, reversible C═N bonds can be well‐integrated into DPNs in combination with permanent covalent crosslinks and/or other dynamic bonds (supramolecular interactions and dynamic covalent bonds), thus outfitting the hydrogels with enhanced mechanical properties, multiresponsiveness, printability, adhesion, and various other functions. This literature review first describes how reversible C═N bonds can be introduced into hydrogels from the perspective of dynamic bonds and network topologies. The design strategies (building blocks, crosslink type combinations, network topologies) reported in the literature are then discussed, as well as the effects of dynamic crosslinking on the hydrogel properties and the potential applications.