Interfacial defect modulation and barrier stabilization in polyurea coatings enabled by polydopamine-functionalized graphene oxide

A polydopamine-functionalized graphene oxide (GO-PDA) nanofiller was synthesized through a one-step self-polymerization process and incorporated into a polyurea (PU) matrix to modulate nanosheet defect states, interfacial chemistry, and macroscopic coating performance. PDA deposition effectively reduces the density of oxygen-related defects on GO, enhances π–π conjugation within the carbon framework, and introduces amine-bearing functionalities capable of forming covalent and hydrogen-bond interactions with isocyanate-derived segments in PU. These molecular-level modifications suppress nanosheet aggregation and promote homogeneous dispersion, yielding a compact hybrid network with strengthened filler–matrix adhesion. The GO-PDA/PU coating exhibits markedly improved mechanical robustness, including an adhesion strength of 16.50 MPa, a tensile strength of 44.6 MPa, and reduced wear-induced mass loss. Furthermore, nanoscale defect passivation and the formation of tortuous diffusion pathways regulate transport pathways and barrier integrity, enabling the coating to maintain impedance values above 10¹¹ Ω·cm² after 150 days of NaCl immersion and remain structurally intact after 3100 h of neutral salt-spray exposure. These findings demonstrate that tailoring GO defect chemistry and polymer–filler interfacial interactions via PDA provides an effective strategy for constructing polyurea-based nanocomposite coatings through interfacial defect modulation and transport-path regulation, enabling sustained physicochemical stability.