A facile approach to durable, transparent and self-healing coatings with enhanced hardness based on Diels-Alder polymer networks

Prolonged durability in outdoor environment and ease of application are highly required features for self-healing coatings. To this end, a novel transparent and self-healing nanocomposite for optical applications, based on Diels-Alder (DA) chemistry is developed in this work. First, a novel, highly soluble, bismaleimide enabled a simple coating fabrication by coupling with furan-functionalized polyacrylates in industrially relevant solvents. The resulting crosslinked coatings exhibited high transparency and complete absence of color, as assessed by UV–vis spectroscopy. Their thermal behavior and the conditions required by the healing process were significantly affected by the degree of furan/maleimide functionality of the system. Secondly, the addition of a small amount of a commercial antioxidant stabilized the optical properties against photo-oxidative weathering, both on clear and titania-pigmented coatings, as determined by colorimetric analysis. Finally, dispersion of silica nanoparticles in the DA-based matrix allowed to enhance the surface hardness of the coatings, while retaining the self-healing ability.