The Interaction of Gemini Surfactants C_(12)-s-C_(12)·2Br with Aqueous Suspension of Fumed Silica

摘要

The interaction of Gemini surfactant C_(12)-s-C_(12)·2Br 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 C_(12)-S-C_(12)·2Br shows strong adsorption ability on the fumed silica. Zeta potential was turned from negative to positive by the addition of small quantitates of C_(12)-S-C_(12)·2Br. 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 1 mmol·L~(-1). These phenomena have never been observed for the systems containing s=4 and s=6.