Polystyrene/montmorillonite nanocomposites were prepared by melt intercalation.Their structure and properties were studied with X ray diffraction and differential scanning calorimetry.X ray diffraction results proved that polystyrene melt could not be intercalated in original Na+ montmorillonite

but could be intercalated in organically modified montmorillonite.The gallery distance of organo montmorillonite increased from 2.16nm to 3.25nm after intercalation of polystyrene chains.The presence of the alkylammonium cations is the galleries of organo-montmorillonite rendered the hydrophilic montmorillonite organophilic.The role of alkylammonium cations was to lower the surface energy of the inorganic montmorillonite and improve the wetting characteristics with polystyrene.The glass transition temperatures of polystyrene/organo-montmorillonite composites for various heating time were all 1～2°higher than that of bulk polystyrene.Also the enthalph changes at glass transition of polystyrene/organo-montmorillonite were larger than that of bulk polystyrene.The results indicated that polystyrene/organo-montmorillonite hybrid formation required no additional processing time than currently required by conventional polymer processing techniques.