Adsorption modeling of polydimethylsiloxane on silica: Using hexamethyldisiloxane as a model probe

Surface interactions play a most important part in the reinforcement of silicone elastomers, owing to the adsorption of the polydimethylsiloxane (PDMS) chain on the filler surface. The impact of the silylation of surface silanol groups on the surface structure and activity is of high technical interest. Hexamethyldisiloxane is an appropriate volatile probe to model the adsorption interactions of the PDMS polymer. In this study we investigated the static-volumetric gas adsorption of hexamethyldisiloxane on hydrophilic and silylated fumed silica, modified by dimethylsiloxy and trimethylsiloxy groups. The degree of silylation was controlled by the silanol content of the silica surface. Adsorption isotherms are discussed in terms of the adsorption energy and the heterogeneity of the active sites of adsorption.