Damage-indicating and self-healing anticorrosion coatings based on fluorescence resonance energy transfer and photothermal shape memory mechanism

Self-healing coatings, which possess the ability to repair damage and restore corrosion resistance without significant human intervention, have become a hot topic in corrosion protection research. In this paper, (±)-10-camphorsulfonic acid-doped polyaniline is synthesized and then combined with copolyurethane (copPU) to form the photothermal shape memory composite polymer (CSPA-copPU). An aggregation-induced emission agent, named N’,2-bis[(E)-5-chloro-2-hydroxybenzylidene] hydrazine-1-carbohydrazide, is synthesized and applied to create a synergistic fluorescence system with a prepared chelation-enhanced fluorescence (CHEF) agent, named Rhodamine Benzimidazole. Under the CHEF behavior in response to Fe3+ and the fluorescence resonance energy transfer effect, the system exhibits a strong and sensitive fluorescence response to corrosion-generated Fe3+. Using electrospinning technology, CSPA-copPU@Fl fibers are prepared with CSPA-copPU as the shell and a mixture of fluorescent agents as the core solution and applied to create the composite coatings. The coatings effectively indicate damage in the form of fluorescence, providing guidance for infrared laser repair. CSPA facilitates the passivation of exposed steel. Under irradiation by an infrared laser, the surface temperature reaches the glass transition temperature of copPU and the epoxy binder. Through softening expansion and diffusion entanglement of molecular chains, scratches in the coatings are closed and repaired, and the corrosion resistance is restored to a level of intact coatings.