pH-activated dynamic ionomer-acetal networks for self-healing and recyclable electrophoretic acrylic coatings

Abstract

Dynamic polymer networks capable of adaptive self-repair and reprocessing are of growing interest for extending the service lifetime of functional coatings; however, achieving such behavior in waterborne electrodeposited systems remains challenging due to restricted chain mobility and ionic screening effects. Herein, we report a pH-activated, vitrimer-like acrylic coating system based on a dual-dynamic network that integrates ionomeric clustering with reversible acetal bond exchange. The coatings are fabricated via cathodic electrophoresis of a lactic-acid-neutralized acrylic ionomer, followed by in situ crosslinking with glutaraldehyde to generate an associative network capable of topological rearrangement without dissolution. The self-healing behavior is strongly governed by environmental pH, with complete crack closure achieved at substantially lower temperatures under acidic conditions. Systematic swelling, spectroscopic, and thermal analyses demonstrate that enhanced protonation of pendant amine groups promotes ionomeric domain expansion and facilitates acetal bond exchange, collectively lowering the activation barrier for network rearrangement. Multiwalled carbon nanotubes were surface-functionalized with a hydrophobic silane and incorporated into the polymer matrix as fillers. This led to the generation of nanoscale roughness in the coating, resulting in a higher contact angle, delayed freezing time and blocked ion pathways, enhancing the anticorrosive properties of the nanocomposite coatings. The MWCNTs maintain the conductive nature of the coating, allowing for secondary electrophoresis on already coated cathodic substrates. This work explores dynamic polymer chemistry and the incorporation of functionalized nanofillers to provide a chemical route for the synthesis of coatings with intrinsic functionalities rather than independent surface treatments to achieve specific properties.