Synergistic “repel-and-kill” strategy in bio-based polybenzoxazine coatings for high-efficiency marine antifouling and anticorrosion

Marine biofouling and corrosion severely damage marine vessels and offshore facilities, creating an urgent need to develop sustainable, non-toxic marine coatings that can offer antifouling and anticorrosion properties. In this study, benzoxazine monomer with benzothiazole and siloxane groups (BM) was prepared through a Mannich reaction (eugenol, paraformaldehyde, and 2-aminobenzothiazole) followed by Michael addition with mercaptopropylsiloxane. The monomer was mixed with hydrophilic polyglycerol (PG) and then thermally initiated the ring-opening polymerization to obtain PG-modified polybenzoxazine (CBM-X) coating. The coating exhibited excellent antifouling effect via “repel-and-kill” mechanism, where the repellent effect is provided by the low surface energy of the cross-linked framework and the robust hydration barrier formed by PG; whereas the kill mechanism is achieved by BTZ functional groups embedded in the network. The anti-adhesion rates against proteins and algae are over 98% and 78%, respectively, while the bactericidal rates against Gram-negative and Gram-positive bacteria are both >98%. Meanwhile, the coating also exhibits excellent corrosion resistance, which can be attributed to the highly dense hydrophobic cross-linked network and the complexation of BTZ on the metal surface. Electrochemical measurements show that the coatings (PG content <10 wt%) have an impedance modulus exceeding 10 8 Ω·cm 2 and nearly ideal capacitance. Moreover, the metal surface morphology remains stable under prolonged salt spray exposure. This study therefore provides a blueprint for creating advanced, eco-friendly protective coatings. Synergistic mechanism of the multifunctional coating for integrated antimicrobial efficacy, antifouling performance, and corrosion barrier protection. • Bio-based polybenzoxazine coatings utilize a synergistic "repel-and-kill" strategy. • Polyglycerol and benzothiazole groups provide robust antifouling and bactericidal action. • Combines outstanding corrosion resistance with efficient antifouling properties.