Multifunctional Fluorinated Polybenzoxazine Coatings with Durable Superhydrophobicity, Anticorrosion, and Oil–Water Separation Capability

In this work, fluoro‐core polybenzoxazine coatings were developed to overcome the limitations of conventional organic coatings towards aggressive corrosion in marine and industrial environments. Bis(benzoxazine) monomers were synthesized using a hexafluoropropane‐based fluorinated diamine combined with allylphenol, phenol, 3,5‐bis(trifluoromethyl)phenol and subsequently cured to form highly crosslinked polybenzoxazine networks. The monomer structures were confirmed by ATR‐FTIR, HRMS, 1 H‐NMR and 13 C‐NMR spectroscopic techniques. Curing behavior depended strongly on phenolic structure, with Ap‐fa exhibited the lowest curing temperature of 234°C, indicating favorable processability. Thermal stability with degradation temperatures above 490°C and char yields reaching 45%. Pronounced superhydrophobic behavior was observed, with water contact angles exceeding 150° and a maximum value of 156° for poly(Fp‐fa). When applied to cotton fabric, the poly(Fp‐fa) coating imparted durable super‐hydrophobicity and enabled efficient oil–water separation, achieving separation efficiencies of above 95%. The coated fabric retained superhydrophobic nature even after exposure to acidic and alkaline media, demonstrating strong chemical durability. X‐ray photoelectron spectroscopy (XPS) analysis further confirmed surface fluorine enrichment and the presence of –CF 3 functionalities, evidencing the formation of a low‐surface‐energy interface. Electrochemical impedance spectroscopy, Tafel polarization and salt spray testing revealed outstanding corrosion protection on mild steel, with inhibition efficiencies up to 99.99%. In addition, all benzoxazines exhibited strong antibacterial activity against Escherichia coli and Staphylococcus aureus up to 25 mm of inhibition zone. The monomer of Fp‐fa coated cotton fabric possesses 17.5 mm, confirmed the activity against both Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352 with the relatively low leaching and high retention indicate sustained functional activity. Overall, fluorinated diamine‐based polybenzoxazines are high thermal stability, super‐hydrophobicity, durable anticorrosive protection and fabric‐level oil–water separation capability within a single coating matrix, making them well suited for demanding marine and harsh environmental applications.