Self-healing and antistatic waterborne polyurethane hybrid coating resulting from hard but reversible Zr-O-Si networks

Abstract

Robust, self-healing waterborne coatings have become the preferred choice in the field of flexible electronic devices owing to their outstanding compliance, restorability, and environmental friendliness. Nevertheless, most of the existing self-healing waterborne polymers exhibit viscoelasticity, irreversible fatigue damage, and the challenge of reconciling self-healing functions with mechanical properties, all stemming from inherent molecular structure contradictions between flexibility and rigidity. Here, we propose a novel strategy that utilizes a nanofiller with dynamic reversible bonds to overcome the self-healing limitations that theoretically demand flexible chain, for achieving both mechanical robustness and self-healing ability in the waterborne polyurethane (WPU) hybrid coating system. We modified tetrapropyl zirconate (TPOZ) with 3-aminopropyltriethoxysilane (APTES) to enhance compatibility between the matrix and inorganic particles, while the formation of dynamic reversible bonds through both condensation hydrolysis endows the self-healing abilities. The WPU hybrid coating was designed by covalently incorporating amino-modified TPOZ (A-ZrO2) into a glycinamide-functionalized WPU network, conferring excellent fracture energy (50.3 kJ/m2), elastic recovery, along with antistatic capability to the coating. Furthermore, the hybrid coating maintains a robust mechanical performance alongside 92.58 % of healing efficiency, exhibiting a potential for flexible electronics application. The hybridization strategy via incorporation of the nanofillers with hard but reversible covalent bond resolves the inherent robustness-healing trade-off, providing exciting thoughts to expand WPU applications.