Visible light triggered controlled formation of rapidly self-healing hydrogels based on thiol-disulfide exchange

The properties of stimuli-responsive hydrogels can be tailored under various external stimuli, but it is difficult to realize the customized adjustment of hydrogel properties since the crosslinking degree in the gelation process is intractable. Here, a visible light triggered thiol-disulfide exchange reaction was applied for constructing disulfide-crosslinked hydrogels from P(EMA-SS-PEG), a poly(ethylene glycol) grafted poly(ethyl methacrylate) derivative with a disulfide linkage as the grafting point. This photochemical method provides mild gelation conditions to handily regulate the morphology, mechanical properties, swelling ratio, and degradation rate of hydrogels by simply varying the irradiation time. Based on this strategy, these disulfide-crosslinked hydrogel coatings showed rapid self-healing in 10 min under ambient conditions, which was dependent on the width of the scratch, temperature, and humidity. Notably, spraying water on these coatings could significantly accelerate the self-healing process of large scratches (360 μm) at room temperature with a self-healing time of 1 hour, enabling the practical application of hydrogel coatings in a natural environment.