The preparation of new hybrid nanocomposites, by emulsion polymerization of styrene in the presence of a reactive organophilic clay, and their characterization are described. The reactive organophilic clay is synthesized by exchanging the inorganic cations in the interlayer structure of a natural clay with the quaternary salt of the aminomethylstyrene. This salt is prepared by a Gabriel reaction starting from the (chloromethyl)styrene. The polymeric matrix of the resulting materials was found to be constituted by polystyrene homopolymer and by a blocky copolymer of styrene and quaternary salt of the (aminomethyl)styrene units. The glass transition temperature of the nanocomposites increase as the percentage of organophilic clay increases, although the average molar masses of the polymeric matrix decrease, because of termination and/or chain-transfer reactions caused by the organophilic clay during the polymerization. Accordingly, the inherent reinforcing action due to the presence of the reactive organophilic clay is higher than the observed one.