pH-responsive polysaccharide-based polymers synergies with h-BN to confer self-healing and barrier properties to waterborne epoxy resins

Abstract

Hexagonal boron nitride (h-BN) has excellent lamellar structure and electrical insulation properties, and excels in improving the corrosion resistance of coatings. By utilizing the abundant hydroxyl and amino functional groups on the polydopamine surface, h-BN is endowed with excellent hydrophilicity. Simultaneously, the polysaccharide polymer MD-GT-CS (MGC), formed by cross-linking maltodextrin (MD), gelatin (GT), and chitosan (CS), was combined with the active sites on the surface of BN@PDA, which conferred pH-responsive functionality to the BN@PDA@MGC hybrid material. In addition, cerium ions were introduced into the carboxyl and amino sites on the MGC surface, resulting in the synthesis of BN@PDA@MGC(Ce) (BPMGC), a hybrid material that combines the layered barrier properties, pH responsiveness, and self-repairing functions. The BPMGC/EP composite coating was prepared by doping the hybrid material with EP. The EIS test results showed that the |Z|_0.01 Hz value of the composite coating reached 1.45 × 10⁹ Ω cm² after 40 d, which is an improvement of four orders of magnitude compared to EP (6.85 × 10⁵ Ω cm²). The results of EIS tests at different pH conditions showed that after 40 d of immersion at pH = 3 and 5, the |Z|_0.01 Hz value decreased by two orders of magnitude, but was still two orders of magnitude higher than that of EP at pH = 7. Meanwhile, the strong self-healing ability of BPMGC/EP was determined by EIS analysis of the scratched coating, salt spray test, SEM and EDS analysis of the corroded area. The experimental results show that the incorporation of BPMGC provides a new method to improve the barrier and self-healing properties of epoxy resins.