Redox-responsive self-healing materials formed from host–guest polymers

Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host–guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host–guest interactions. We employ cyclodextrin (CD) as a host molecule because it is environmentally benign and has diverse applications. A transparent supramolecular hydrogel quickly forms upon mixing poly(acrylic acid) (pAA) possessing β-CD as a host polymer with pAA possessing ferrocene as a guest polymer. Redox stimuli induce a sol−gel phase transition in the supramolecular hydrogel and can control self-healing properties such as re-adhesion between cut surfaces. Stimulus-responsive hydrogels have previously been developed that display heat-, light-, pH- or redox-induced sol–gel transitions. Nakahataet al. develop a self-healing supramolecular hydrogel based on host–guest polymers in which redox potential can induce a reversible sol–gel phase transition.