Photothermal self-healing polyurethane coating based on hollow nanofillers in seawater

Herein, a novel composite coating with excellent self-healing and corrosion resistance activated by photothermal responsive hollow core-shell nanofillers was developed. A photothermal nanofiller (Co₉S₈@Bi₂S₃) with a hollow core-shell structure was synthesized and then added to polyurethane (PU) to prepare PU-Co₉S₈@Bi₂S₃ composite coating. Applying 808 nm near-infrared irradiation induces a photothermal effect in Co₉S₈@Bi₂S₃, which subsequently initiates the reconstruction of reversible hydrogen bonds, facilitating the self-healing of coating scratches. The excellent photothermal self-healing performance of PU-Co₉S₈@Bi₂S₃ coating was demonstrated by scratch tests and molecular dynamics simulations. The electrochemical impedance spectroscopy test results showed that the PU-Co₉S₈@Bi₂S₃ coating has good self-healing and anti-corrosion properties. The low-frequency impedance modulus of the coating after three self-healing sessions was still close to 10⁹ Ω·cm² after 30 d of immersion in seawater. This study provides a new strategy for developing multi-cycle self-healing coatings triggered by photothermal effects.