Vinyl monomer-montmorillonite intercalates, which are able to swell and disperse in organic solvents, have been prepared by a cation exchange process by the interaction between the Na+ or Ca2+ cations of montmorillonite and vinylbenzyltrimethylammonium chloride. The resulting vinyl monomer-montmorillonite materials have been identified by X-ray diffraction (XRD), elemental analysis and infrared absorption spectra. Free-radical solution polymerizations of the penetrated styrene between the interlayers of 5, 10, 25 and 50 wt% vinyl monomer-montmorillonite have resulted in grafted polystyrene-montmorillonite materials. The effect of montmorillonite amounts on the formed polystyrene was determined by extraction with organic solvents, which showed an increase in the grafted polymer formed (0.84-2.94 g/g MMT), and a decrease in the external polystyrene with increasing amounts of montmorillonite. The molecular weight of the external polystyrenes was found to be in the range of 22 000. The vinyl monomer-montmorillonite and polymer-montmorillonite intercalates have been identified by XRD, elemental analysis and infrared spectroscopy. Examination of the polystyrene-montmorillonite materials by SEM, TEM and XRD showed spherical particles of nanosize about 150-400 nm, and basal spacings of 1.72-2.45 nm.