Surfactant bilayers adsorbed on silica are used as the reaction site for the formation of ultrathin polymer films from coadsorbed or adsolubilized monomer. Results from the polymerization of styrene in cetyltrimethylammonium bromide (CTAB), in octylphenoxypoly(ethoxy)ethanol, and in methyltri(C8-C10)ammonium chloride bilayers show effective conversion of adsolubilized styrene monomer to polystyrene. The process has been demonstrated effective with amorphous precipitated silica substrates having a variety of surface areas and with two types of initiation schemes. The extractable polymer has been characterized using photoacoustic FTIR, UV, and gel permeation chromatography (GPC). Only approximately 25% of the polymer was extractable after refluxing for 4 h in tetrahydrofuran. The impact of the treatment on some industrially important surface properties of the modified silicas has also been determined. The process offers a potentially inexpensive method for modifying chemical and physical surface properties of various substrates.