Mechanochromic and thermally reprocessable thermosets for autonomic damage reporting and self-healing coatings

Autonomous polymers that report damage prior to loss of function and simultaneously self-heal are highly relevant for preventing catastrophic failures and extending the lifetimes of materials. Here, we demonstrate mechanochromic and thermally reprocessable thermosets that can be used for autonomic damage reporting and self-healing coatings. A mechanochromic molecule, spiropyran (SP), is covalently incorporated into thermoreversible Diels-Alder (DA) cross-linking networks. Mechanical activation of SPs in DA networks is confirmed by computational simulations and mechanical testing. The damaged areas of the polymers change colour, emit fluorescence signals, and completely recover after heat treatment. Because of the thermoreversible covalent networks, these polymers can be recycled up to fifteen times without degrading their mechanical, damage-reporting, or self-healing properties. Our autonomic material systems provide a new way to enhance the lifespans and reliabilities of thermosetting coatings, which also expands the range for practical applications of force-induced chemical reactions in polymers.