Self-healing polyurethane coatings based on dynamic chemical bond synergy under conditions of photothermal response

Self-healing coatings represent a promising advancement in intelligent materials, as they possess the ability to autonomously heal damage through a self-regeneration mechanism. However, a significant challenge is to strike a balance between the self-healing capability and mechanical performance under specific healing conditions, such as heat or light. This limitation hinders the application of self-healing coatings. This study describes a series of syntheses of a waterborne polyurethane (WPU) based on a vanillin-derived aromatic Schiff base (VASB). The VASB-WPU was created by incorporating dynamic reversible covalent bonds into the backbone chain and introducing supramolecular interactions (hydrogen bonds and ionic bonds) into the side chain. The VASB-WPU exhibits self-healing properties and vitrimer characteristics. By implementing a healing process that involves light and heat stimulation, the VASB-WPU exhibits an impressive healing efficiency of 92.43% in thin films while maintaining exceptional mechanical performance, with a tensile stress of 10.59 MPa and a toughness of 16.56 MJ/m3. Furthermore, the VASB-WPU coatings exhibit exceptional multiple shape memory capabilities and self-healing effects. When applied to wooden surfaces, the VASB-WPU coatings can achieve 100% self-healing of a 5 μm scratch at the interface in just 3 min of irradiation. A new method has been introduced for developing intelligent self-healing coatings for wood.