Poly(dimethylsiloxane) (PDMS)/clay nanocomposites have been synthesized using a novel w-ammonium functionalized oligo-PDMS surfactant (PDMS-N+(CH3)(3)) and processed in membrane form. In order to relate the clay morphological structure to the degree of dispersion and physical properties of the membrane, the clay ion-exchanged by PDMS-N+(CH3)(3) has been compared to a non-exchanged sodium MMT and to two organoclays organo-modified by using either non-functional alkyl ammonium cations (C38H80N+) or hydroxyalkyl ammonium (C22H48ON+) cations. Morphological analysis and transport properties (sorption, diffusion and permeability) have been investigated using two penetrants: acetone and n-hexane. The mechanical and theological properties of the PDMS nanocomposite membranes have also been studied. It has been found a significant effect of the clay organo-modifier on the morphology, physical and barrier properties of the systems. (C) 2008 Elsevier Ltd. All rights reserved.