Rapid Self-Healing of Robust Surface-Tethered Covalent Adaptable Coatings

The incorporation of self-healing properties to repair scratches (or other minor damage) has revolutionized the coating industry by increasing service life, sustainability, and optical appearance. This work addresses challenges with the robustness of self-healing coatings through the inclusion of surface-tethered covalently adaptable networks (CANs). Surface-initiated polymerization is combined with spray-coating to deposit polymers to produce coatings with reversible crosslinks to the tethered chains. These robust coatings are based on reversible vinylogous urethane bonds using 2-(acetoacetoxy)ethyl methacrylate-based polymers and tris(2-aminoethyl) amine (TREN). Here, TREN enables reversible covalent bonding between the spray-coated and surface-tethered polymers. Without this polymer brush layer, the physisorbed CAN coatings fail to self-heal completely, are labile to solvent, and exhibit shear delamination upon scratching. The utility of this tethered coating approach is highlighted through its ability to autonomously self-heal incisions within seconds at elevated temperatures, or more steadily under ambient conditions. The key to these advancements is the use of polymer brushes as a primer layer to attach the CAN to enhance healing and improve the environmental robustness of the coating.