Nanocomposites were prepared by butyl acrylate graft polymerization from montmorillonite-type layered silicates. Successful polymer grafting required novel dialkyl peroxides comprising two cationic ammonium groups, which were intercalated in the layered silicate by cation exchange. Thermal cleavage of the peroxide functionality in the presence of butyl acrylate as monomer initiated polymerization and hence exfoliation of the layers. Detailed examination of this process shows that the polymerization cannot be controlled by external nitroxides.