SURFACE MODIFICATION OF COLLOIDAL SILICA SOL WITH LONG-CHAIN FATTY ACIDS: INTERFACIAL INTERACTIONS, COLLOIDAL STABILITY, AND HYDROPHOBIC PROPERTIES

Long-chain fatty acids may alter the wettability and interfacial behavior of colloidal silica, but adsorption, free-acid deposition, and covalent grafting are often conflated. This article critically reviews evidence concerning palmitic (C16:0), stearic (C18:0), and oleic (C18:1) acids and proposes a reproducible framework for evaluating modification while retaining dispersion stability. Published findings support hydrogen bonding and physical adsorption as plausible interactions on unactivated silica. Oleic-acid-treated silica has stabilized approximately 200 nm Pickering emulsion droplets, while a silica–stearic-acid coating system showed a water contact angle of 142 ± 6°; alumina activation has separately increased stearic-acid attachment. These results refer to different material configurations and are not directly comparable. A controlled study combining FTIR, dynamic light scattering, electrophoretic mobility, thermogravimetry, adsorption mass balance, and contact-angle measurements is recommended. pH, modifier loading, solvent composition, ionic strength, and acid unsaturation should be controlled. Durable modification should be claimed only when retained surface species and application-level effects are demonstrated after washing and storage.