The Interaction of Gemini Surfactants C12-s-C12·2Br with Aqueous Suspension of Fumed Silica

The interaction of Gemini surfactant C12-s-C122Br with aqueous suspension of fumed silica have been investigated by DLS, Zeta potential, conductivity, pH value and fluorescence. With the increase of surfactant concentration, four regions exist during the adsorption and aggregation process, which can be recognized as ion exchange adsorption, electrostatic repulsion, adsorption layer formation by hydrophobic interactions and free micelle formation. The Gemini surfactant C12-s-C122Br shows strong adsorption ability on the fumed silica. Zeta potential was turned from negative to positive by the addition of small quantitates of C12-s-C122Br. The “dispersion-flocculation-dispersion” phenomena was observed for the addition of s=2 during 0.1 to 4 mmol L-1. 5% fumed silica dispersion system can be gelled by s=2 of 1mmol L-1. These phenomena have never been observed for the systems containing s=4 and s=6.