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

TLDR

Self‑healing materials are increasingly sought to extend material lifespans, and host–guest supramolecular chemistry offers a powerful route to stimulus‑responsive hydrogels that can undergo sol–gel transitions in response to heat, light, pH, or redox cues. The study aims to develop a redox‑responsive, self‑healing supramolecular hydrogel formed by host–guest polymer interactions that enable reversible sol–gel transitions. The hydrogel is formed by mixing β‑cyclodextrin‑functionalized poly(acrylic acid) with ferrocene‑functionalized poly(acrylic acid), yielding a transparent network that undergoes a redox‑induced sol–gel transition and allows self‑healing through re‑adhesion of cut surfaces. The study is reported by Nakahata et al.

Abstract

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.