Supramolecular polymer network gels constructed by a pillararene-containing polymer and their applications in adhesion between semihard materials

Adhesion between hard materials without any glue is challenging and difficult. Supramolecular chemistry provides an innovative and feasible solution to realize such adhesion via non-covalent interactions. Here, we realized adhesion between semihard materials via host-guest interactions and metal coordination based on a copolymer with pillar[5]arene and 4-pyridinemethoxy ester as the side chains. The copolymer can form two supramolecular polymer network gels crosslinked either by the host-guest interactions between pillar[5]arene and 4-pyridinemethoxy ester under acidic conditions or by the metal coordination between 4-pyridinemethoxy ester and Cu(ii) under neutral conditions. The supramolecular polymer network gels based on host-guest interactions or metal coordination displayed pH- or cyanide-responsiveness, respectively. Interestingly, these two gels can reversibly interconvert by regulating the pH condition. Additionally, they were both responsive to UV light due to the photolysis of the 4-pyridinemethoxy ester group. Furthermore, these two gels can both achieve adhesion under semihard conditions. The ruptured xerogels can rejoin quickly after dropping a minimal amount of chloroform onto the fractured surface, with non-covalent interactions as the driving forces.