(183e) Stability of Surfactant Stabilized Emulsions to the Addition of Fumed Silica Suspensions

We investigated the stability of oil-in-water emulsions stabilized with SDS(anionic), CTAB(cationic) and Triton X-100(non-ionic) surfactants, to the addition of negatively charged fumed silica suspensions. The final stability and structure of the emulsion droplets were determined by surfactant-particle interactions, mixing conditions and the concentration of particles in the bulk. Simple addition of fumed silica particles does not have any effect on the stability of the SDS stabilized emulsions. Coalescence of emulsions droplets is observed when fumed silica particles were added to emulsions stabilized with Triton X-100 molecules. In case of emulsions stabilized with CTAB, addition of fumed silica particles resulted in coalescence and phase separation of oil-water phase (or) formation of particle coated droplets, depending on the final concentration of silica particles in the solution. Vortex mixing of emulsions after the addition of particles resulted in the synergistic stabilization of emulsion by both particles and surfactants. Fractional coverage of the particles on the droplet surfaces was varied depending on the surfactant-particle interaction and particle concentration in the bulk. Cryo-SEM and fluorescence confocal microscopy were used to determine the final structure of the emulsion droplets and zeta potential measurements were used to support the above findings.