An account of the experiments on preparing polystyrene(PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported.Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety.Because the reaction may liberate HC1,it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H~+ ions.Only the silanol groups on the edge of the clay react with vinyltrichlorosilane.The radical polymerization of the product with styrene as a vinyl monomer leads to chemical grafting of PS onto the montmorillonite surface.The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction.Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy.The prepared nanocomposite materials and the grafted nano-particles were studied by XRD.Exfoliated nanocomposites may be obtained for 0.5 wt%-l wt%clay content.The nanocomposites were studied by thermogravimertic analysis(TGA) dynamic thermal analysis(DTA) and dynamic mechanical analysis (DMTA). An account of the experiments on preparing polystyrene (PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported. Closer 20A was mixed with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Abstract of the reaction may liberate HC1, it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H ~ + ions. Of the silanol groups on the edge of the clay react with vinyltrichlorosilane. radical polymerization of the product with styrene as a vinyl monomer to chemical grafting of PS onto the monmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nanocomposite materials and the grafted nano-particles were studied by XRD. Exfoliated nanocomposites may be for 0.5 wt % -l wt% clay content. The nanocomposites were studied by thermogravimertic analysis (TGA) dynamic thermal analysis (DTA) and dynamic mechanical analysis (DMTA).