Dynamic Hydrogels with an Environmental Adaptive Self-Healing Ability and Dual Responsive Sol–Gel Transitions

Dynamic polymer hydrogels with an environmental adaptive self-healing ability and dual responsive sol–gel transitions were prepared by combining acylhydrazone and disulfide bonds together in the same system. The hydrogel can automatically repair damage to it under both acidic (pH 3 and 6) and basic (pH 9) conditions through acylhydrazone exchange or disulfide exchange reactions. However, the hydrogel is not self-healable at pH 7 because both bonds are kinetically locked, whereas the hydrogel gains self-healing ability by accelerating acylhydrazone exchange with the help of catalytic aniline. All of the self-healing processes are demonstrated to be effective without an external stimulus at room temperature in air. The hydrogel also displays unique reversible sol–gel transitions in response to both pH (HCl/triethylamine) and redox (DTT/H2O2) triggers.