Underwater Adhesive HPMC/SiW-PDMAEMA/Fe3+ Hydrogel with Self-Healing, Conductive, and Reversible Adhesive Properties

A reusable, underwater adhesive, self-healing, and conductive hydrogel was developed by the construction of an interpenetrating network structure consisting of a tungstosilicic acid (SiW) cross-linked hydroxypropyl methylcellulose (HPMC) network and a ferric ion cross-linked poly(dimethylaminoethyl methacrylate) (PDMAEMA) network. The impacts of HPMC, SiW, DMAEMA, and ferric chloride content on adhesion properties were carefully evaluated. The results demonstrated that the 3–2–0.5–60 hydrogel showed the optimal shear adhesion strength. The obtained HPMC/SiW-PDMAEMA/Fe3+ hydrogels exhibited reusable adhesion on the surfaces of various materials such as glass, wood, metals, agate, plastics, ceramics, and rubber. It was noticed that the HPMC/SiW-PDMAEMA/Fe3+ hydrogels also displayed attractive underwater adhesion performance, and they could be adhered to various substrates underwater without any pretreatment or long curing time. In addition, the HPMC/SiW-PDMAEMA/Fe3+ hydrogel showed strain-responsive conductivity and outstanding self-healing performance. Therefore, this work developed a simple method to fabricate reusable, underwater adhesive, conductive, and self-healing hydrogels, which ensure the hydrogel’s broad applicability.