Bio-based multifunctional coatings for cotton fabrics: integrating flame retardancy, antibacterial and hydrophobic properties

Abstract Cotton fabrics offer excellent comfort and biodegradability, but suffer from high flammability and poor antibacterial properties, limiting their use in safety–critical applications. Herein, a multifunctional modification strategy is proposed: phosphonated hyaluronic acid and quaternized chitosan are synthesized to form a flame-retardant and antibacterial coating on cotton fibers via layer-by-layer (LbL) self-assembly, followed by hydrophobic modification using tetraethyl orthosilicate and hexadecyltrimethoxysilane. The modified fabrics exhibit a 14.5% coating add-on, a charred length of 8 cm, self-extinguishing behavior, and an 83.3% reduction in peak of heat release rate compared to untreated cotton. The treated cotton fabrics retain over 90% of their tensile strength with minor reductions in elongation, while their air permeability shows only minor reductions due to partial pore blocking. Antibacterial efficacy reaches 99.9% against Escherichia coli and Staphylococcus aureus . Hydrophobic treatment yields a water contact angle > 150°, conferring superhydrophobicity, self-cleaning, and stain resistance. At the same time, the treated cotton fabric shows good washing durability. This work develops a scalable, multifunctional strategy for modifying cotton fabric, integrating the molecular design of bio-based flame-retardant and antibacterial polyelectrolytes with layer-by-layer (LbL) self-assembly and a non-halogenated siloxane-based hydrophobic modification, providing a technical reference for the design and development of high-performance multifunctional textiles.