Harnessing mechanochemical fluorescence toward autonomous damage-reporting coatings†

Abstract

Protective coatings are essential for shielding engineering materials from environmental and mechanical damage. A significant endeavor in this regard is detecting the damage in coatings and implementing necessary repairs. However, conventional detection methods often require specialized equipment and expertise, rendering them impractical for real-time monitoring. This work introduces an autonomous damage-reporting coating system based on a stress-responsive polymer network containing a Diels–Alder adduct mechanophore. When subjected to mechanical damage, the mechanophore undergoes a retro-Diels–Alder reaction, liberating a fluorescent π-extended anthracene moiety. The mechanically triggered “off-to-on” optical signal allows for highly sensitive detection of material damage preceding failure. A quantitative relationship between the extent of impact damage and the mechanochemically generated fluorescence is established, facilitating the prediction of material failure. Remarkably, the damage-reporting functionality is maintained even after incorporating pigments into the coating formulation, thereby broadening the applicability of this smart coating system in real-world scenarios.