Anti-corrosion coating within a polymer network: Enabling photothermal repairing underwater

Designated repairing of a damaged anti-corrosion coating underwater remains a big challenge because of the requirements on both fluidity and stability of the coating in water during repairing, as well as the water resistance for corrosion prevention. Herein, we develop a novel composite coating by confining the paraffin wax (PW) within a polypropylene (PP) network fabricated through thermally induced phase separation (TIPS). Integrating with the carbon-based photothermal agents, PW experiences a solid-to-liquid transition at an elevated temperature caused by photothermal effect and flows across the PP network to the damaged region. The PP network plays a crucial role in preventing the detachment of molten PW from the substrate by reserving it through capillary and hydrophobic interactions. Such a bicontinuous structure enables fast, designated and repeatable in-situ repairing underwater under a near-infrared (NIR) laser, and the coating exhibits outstanding corrosion resistance before damage and after repairing.