Diels–alder/disulfide dynamic covalent FEVE networks with coupled self-healing and surface charge regulation

Dynamic covalent networks provide a practical route to repairable coatings, but combining damage recovery with surface charge regulation remains difficult in fluoropolymer systems. Here, fluoroethylene vinyl ether copolymer (FEVE) coatings were crosslinked through NCO–OH reactions using isophorone diisocyanate (IPDI)-based curing agents containing Diels–Alder (DA) and disulfide (S–S) structures. Variable-temperature Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) showed clear temperature-responsive behavior in the cured networks. The DA7-2S3 coating, prepared at a 7:3 M ratio of DA-type to S–S-type curing components, had a glass-transition temperature of 27.3 °C, below the healing temperature of 70 °C. Quantum chemical calculations and surface electrical measurements showed that the dynamic structures altered localized states and charge-transport behavior. Pure DA exhibited deeper trap characteristics and the highest initial characteristic flashover voltage of 11.51 kV, but retained 92.98% after damage–healing. DA7-2S3 reached an apparent scratch-healing efficiency of 86.8%, while its characteristic flashover voltage decreased only from 11.28 to 11.02 kV, corresponding to 97.67% retention. Adjusting the DA/S–S ratio therefore improved the balance among charge regulation, damage recovery, and post-healing insulation retention.