A novel method for preparation of exfoliated/intercalated nanocomposites is reported based on two steps, i.e. preparation of treated-montmorillonite (MMT) solution and solution blending with polymers. After in situ polymerization of dimethyldichlorosilane between layers and separation of most polydimethylsiloxane (PDMS), the treated-MMT solution shows good storage stability. Although elemental analyzer shows no residue PDMS, NMR proves residue PDMS still exists in the solution. The residue PDMS is believed to graft onto the MMT layer surface via condensation of hydroxyl groups of PDMS and those that existed on MMT surface. Lower relaxation time of end-capped CH3 of alkyl ammonium grafted onto layer surface via ion exchanging in the solution shows that the layer spacing was increased significantly or even exfoliated. When the solution was blended with some polar polymers, exfoliated nanocomposites were found. When it was blended with some nonpolar polymers, however, intercalated nanocomposites were obtained. The reason was explained in the light of compatibility between polymer matrix and MMT as well as alkyl ammonium and PDMS grafted on the layer surface. For intercalated nanocomposites, different layer spacing corresponds to different chain flexibility and the presence of multi-peaks is caused by the processing of these blends. (C) 2003 Elsevier Science Ltd. All rights reserved.