Design principle for solvent and abrasion resistant polydopamine coating: Intra- vs inter-particle crosslinking via UV-induced nitrene CH insertion

Bio-inspired polydopamine (PDA) coatings provide substrate-independent deposition via a simple aqueous dip-coating process but suffer from poor stability in strong alkaline and polar aprotic solvents and are vulnerable to abrasive damage because their assembly is dominated by cation–π and other secondary interactions rather than robust covalent bonding. Existing stabilization strategies often improve solvent resistance without enhancing mechanical durability or increase toughness at the expense of hydrophilicity or by requiring harsh annealing conditions incompatible with sensitive substrates. Here, we introduce a UV-activated, nitrene-generating crosslinker, polyethyleneimine benzoic azide (PEIBA), designed to associate with PDA via polyamine–catechol interactions and, depending on the processing route, to form intra- or interparticle covalent linkages upon activation. UV-irradiated, co-deposited PDA–PEIBA coatings mainly undergo intraparticle crosslinking, and under the optimized conditions, they retain over 90% surface coverage after exposure to aggressive solvent tests. In contrast, post-modified PDA coatings treated with PEIBA produce interparticle crosslinking and preserve 90% of the coating after 1000 abrasion cycles while also exhibiting excellent solvent resistance, compared with the complete delamination of pristine PDA after only 20 cycles. Notably, the static water contact angle of the post-modified PDA–PEIBA coating remains at 36.2° after UV irradiation, indicating that moderate hydrophilicity is preserved. Collectively, this work elucidates a generally applicable crosslinking strategy for producing PDA coatings with substantially enhanced solvent and abrasion resistance while maintaining desirable wettability in aqueous environments.