The adsorption of polyoxyethylene alkyl ether surfactants (Brij 30 and Brij 35) on synthetic smectite clay (Laponite) nanoparticles and the interactions between them have been investigated through surface tension, zeta potential and rheology properties measurements, showing that Brij 30 and Brij 35 are adsorbed onto Laponite surface, and the adsorption is increased with decreasing oxyethyl groups (EO). The zeta potential of the Laponite decreases slightly at the high Brij concentrations, and the rheology results indicate that the adsorption of Brij reduces the particle-particle interactions and the viscosity. Brij surfactants and Laponite nanoparticles were used to prepare emulsions containing equal volumes of oil and water. The emulsion stability and droplet size measurements indicate that the properties of the emulsions are mainly controlled by the Laponite at low Brij concentrations, whereas primarily depend on the Brij concentrations at high surfactant concentrations. To illuminate the different effects between cationics (such as CTAB) and Brij on emulsions stabilized by negatively charged solid particles, the desorptions caused by high speed shear were measured.

Key words: synthetic smectite clay, Adsorption of polyoxyethylene alkyl ether surfactants, rheology, adsorption, emulsion