Photothermal-triggered shape memory coatings with active repairing and corrosion sensing properties

Smart polymeric materials with outstanding self-healing and corrosion reporting capability are highly desirable for next-generation anticorrosion coatings, which can timely and autonomously repair coating scratches and sense corrosion occurrence. Herein, a distinctive multifunctional composite coating is constructed by incorporating graphene-based nanosheets (polydopamine@graphene oxide loaded with 1,10-phenanthrolin-5-amine) into thermal-responsive shape memory polymers. Benefiting from the photothermal characteristics of graphene oxide and polydopamine, the coating displays rapid crack closure behaviors under near-infrared irradiation, and the released 1,10-phenanthrolin-5-amine (NH2-Phen) also simultaneously chelates with Fe2+ ions to resist further substrate corrosion in saline solution. The combination of intrinsic and external healing mechanisms endows the coating with enhanced repairing ability, aiming to repair wider cracks. Moreover, the formed Phen-Fe complex exhibits conspicuous fluorescence quenching to report early corrosion, which is more visualized and applicable in graphene-based dark coatings. As a proof-of-concept, the scratched coatings exhibit a rapid NIR response within 90 s of irradiation and visible fluorescence changes after immersing in 3.5 wt% NaCl solution for 1 h. The active protection ability of composite coatings is further demonstrated via electrochemical tests and corrosion product characterization. These multifunctional coatings provide a useful strategy for engineering smart protection materials with high healing efficiency and sensitive corrosion reporting capability in the anticorrosion field.