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

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.