A functionalized graft copolymer (poly(styrene-butadiene-styrene) (SBS)-g-4-benzoyl-N,N-dimethyl-N[2-(2-methy1-1-oxo-2-propenyloxy)ethylib enzenemethanaminium bromide (4-BBPDMAEMA)}, containing a photoinitiator, quaternary ammonium cations, and many C=C double bonds, was synthesized to modify clays, such as Na+-montmorillonite (MMT) clay, for the preparation of organic-inorganic nanocomposite resins via radical photoinduced crosslinking polymerization. The structure of SBS-g-4-BBPDMAEMA was characterized by Fourier transform infrared and H-1-NMR spectroscopy. The corresponding SBS-g-4-BBPDMAEMA was found to have two functions: the capability to ionically exchange with sodium ions in the silicate gallery and the capability to synthesize exfoliated SBS/MMT nanocomposites by the UV crosslinking of intercalation polymerization. The results from the X-ray diffraction primarily reveal that the clay platelets should have been exfoliated or completely disordered. However, the results from transmission electron microcopy confirmed that a mixture of partially exfoliated and intercalated structures presented in the nanocomposites. Dynamic mechanical thermal analysis testing indicated that the glass-transition temperature of the polybutadiene phase and polystyrene phase moved to a lower temperature. Data of thermogravimetric analysis and testing of the mechanical properties showed that the thermal stability and mechanical properties of SBS-g-4-BBPDMAEMA could be regulated by the crosslinking and content of MMT. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1675-1682, 2010