Multifunctional and sustainable vitrimer systems for self-healing, scratch resistance, and corrosion protection

Bio-based covalent adaptable networks represent a promising platform for the development of sustainable protective coatings combining durability, self-healing, and end-of-life management. In this work, we report a solvent-free, photocurable vitrimeric system based on bio-derived building blocks incorporating dynamic imine bonds, enabling intrinsic self-healing. The resin, synthesized from methacrylated vanillin and a flexible diamine, and diluted with methacrylated eugenol, was UV-cured in the presence of functionalized silica nanoparticles to form crosslinked composite networks in which the nanoparticles were covalently integrated. The resulting composite systems displayed homogeneous nanoparticle dispersion and tunable properties as a function of filler content. Notably, the incorporation of 2% w/w functionalized silica nanoparticles enabled complete healing in less than five minutes at temperatures as low as 80 °C without external pressure, while simultaneously imparting enhanced scratch resistance. When applied as coatings on steel substrates, pull-off adhesion tests revealed high adhesion strength for all formulations, with no evidence of coating-substrate interfacial failure. Electrochemical impedance spectroscopy measurements showed that pristine coatings provided excellent corrosion protection on steel substrates, maintaining impedance moduli above 107 Ω cm2 after prolonged exposure to saline environments, whereas higher nanoparticle loadings reduced the barrier performance due to increased water uptake. Importantly, the coatings were fully removed from substrates in a diamine solution by exploiting transimination reactions of imine functionalities with diamines, allowing recovery of oligomeric fragments and clean substrate regeneration.