Enhancing superhydrophobicity of paper via gas-phase silylation using hexadecyl- trimethoxysilane and titanium(IV) isopropoxide

The shift toward paper-based packaging is driven by concerns over the non-biodegradability and environmental impact of plastics. Although paper is biodegradable, its poor water resistance limits broader applications. This study aimed to improve the water resistance of paper through chemical vapor deposition (CVD) silylation using different volumes of hexadecyltrimethoxysilane (HDTMS) in the gas phase, which enables deeper penetration into the paper structure than conventional surface coatings. Titanium (IV) isopropoxide (TTIP) was applied as a catalytic primer via spray coating at various concentrations. The results showed that HDTMS alone, at 28 mL·m‒2, produced a hydrophobic surface with a water contact angle of 115° on both sides of the paper. Incorporating 10% v/v TTIP and applying a 30 min vapor deposition generated a superhydrophobic surface, increasing water contact angle from 0° (untreated) to 151° and reducing the Cobb value from 435 g·m‒2 to 17 g·m‒2 on both sides of the paper. Meanwhile, the treated paper maintained water vapor and oxygen permeability comparable to the untreated sample. FT-IR, XRF, AFM, and SEM analyses confirmed successful silylation. Overall, the gas-phase silylation approach effectively enhanced water resistance while maintaining vapor permeability, showing promise for developing breathable waterproof paper for medical, healthcare, and fresh-produce packaging applications.