Molecular simulations of individual and competitive adsorption of water and PDMS (polydimethylsiloxane) on an amorphous silica surface in the temperature range 300-1500 K show that the presence of PDMS does not appear to change the adsorption behavior of water significantly but that the presence of water has a substantial effect on the adsorption behavior of PDMS at temperatures below approximately 600 K. Water adsorbs adjacent to and penetrates into the silica surface while PDMS adsorbs adjacent to the water layer. Finally, the vapor pressure is enhanced at low temperatures because of the formation of nanoclusters on the surface as a consequence of the Gibbs-Thomson effect. (C) 2011 Elsevier B.V. All rights reserved.