pH-responsive intrinsic self-healing coating via in-situ confined solid-liquid transition of hydrogel microdomains

Inspired by pH variation in corrosion microenvironment and the emerging solid-liquid composite strategies, this study presents an innovative self-healing coating based on pH-responsive confined solid-liquid transition behavior, with anti-corrosion functionality as a proof of concept. The coating integrates poly (vinyl alcohol) (PVA) crosslinked with boronic acid (BA) through an in-situ solvent exchange process, forming borate ester-based, pH-responsive PVA-BA (AB) hydrogel microdomains within a poly (3-(trimethoxysilyl) propyl methacrylate) (PTPM) network. The AB/PTPM coating achieves healing within 30 min, based on gel-sol transitions of the AB hydrogel microdomains triggered by different pH conditions (pH = 7 and 11). The hydrophobic PTPM network prevents AB hydrogel microdomains from water intrusion. This design balances the fluidity and stability, providing a solution to enhance the durability of protective coatings. The AB/PTPM coating was applied as a topcoat over an epoxy (EP) primer, and the formed bilayer AB/PTPM@EP coating exhibits excellent anti-corrosion restoration properties after self-healing.