Poly(β-hydroxyether–naphthoxazine)/TiO₂ nanocomposite coatings for cotton fabrics with enhanced UV protection, hydrophobicity, and selective antibacterial activity

Abstract Nanocomposite coatings have developed as promising surface-engineering materials for imparting multifunctional properties to textile fabrics, owing to the synergistic effects of their organic and inorganic components. In this study, a β-hydroxyether-naphthoxazine (βhE-NZ) oligomer was prepared by the catalyst-free oligomerization of a difunctional hydroxyl-functional naphthoxazine monomer (NZ-OH) with bisphenol A diglycidyl ether (BADGE), as confirmed by NMR and FTIR spectroscopy. Incorporation of 3 wt% TiO₂ nanoparticles yielded a nanocomposite with Td₅ and Td₁₀ values of 312 and 369 °C, respectively, and a char yield of approximately 60% at 800 °C, indicating good thermal stability and intrinsic flame-retardant character. Cotton fabrics were treated by dip-coating followed by thermal curing. XRD, SEM, EDX, and AFM analyses verified uniform coating deposition, successful TiO₂ dispersion, and increased nanoscale surface roughness. The cured poly(βhE-NZ)/TiO₂ coated cotton fabrics showed outstanding UV-protection factors (UPF 127 for UV-B/C and 118 at 350 nm) that remained in the excellent range after ten laundering cycles. The water contact angle increased from 81° for uncoated cotton to 128° after nanocomposite coating, confirming enhanced hydrophobicity attributed to the low-surface-energy polymer matrix and hierarchical surface topography. Mechanical testing showed that the nanocomposite coating raised tensile strength from ~ 13 MPa to 17.5–18 MPa while increasing elongation at break, confirming improved strength. Antibacterial assays revealed potent, selective activity against S. aureus (≈ 6-log reduction) with no measurable effect against E. coli . Overall, the poly(β-hydroxyether-naphthoxazine)/TiO₂ nanocomposite provides a versatile, wash-durable surface treatment that integrates high UV shielding, hydrophobicity, mechanical reinforcement, and selective antibacterial performance, offering strong potential for advanced protective textiles.