Results from molecular dynamics (MD) simulations in the interfacial region of three polysiloxanes, polydimethylsiloxane (PDMS), polyoctylmethylsiloxane (POMS) and polymethylphenylsiloxane (PMPhS), and ethanol/water mixtures are reported. The behaviour of all polysiloxanes in contact with the same solvent composition is very similar. The ethanol molecules accumulate at the surface of the polysiloxanes and the polymers begin to swell. The diffusive movement of these partly sorbed ethanol molecules is strongly hindered in the direction of the water phase. Parallel to the polymer surface the diffusion of the ethanol is faster but still slower than in the free diffusion case. The ethanol molecules in the interfacial layer show a favourite orientation wherein the hydrophobic parts point in the direction of the polymer and the hydrophilic parts point in the direction of the water molecules. The ethanol concentration of the feed has a strong influence on the interfacial behaviour.