(216c) Stability and Flocculation Behavior of Silica Microparticles in Ionic Micellar Solutions

Using the technique of colloid probe atomic force microscopy (CP-AFM), measurements of the equilibrium depletion force between a silica particle and a flat silica plate in solutions of tetradecyltrimethylammonium bromide (C₁₄TAB) and sodium dodecyl sulfate (SDS) at varying concentrations were performed. With increasing surfactant concentration, the onset of a depletion well and structural forces was observed implying the possibility of depletion induced flocculation or stabilization in dispersions of colloidal silica. The force versus separation curves obtained through CP-AFM were converted into energy versus separation curves and the stability ratio analysis described by Marmur (J. Colloid Interface Sci. 1979, 72, 41-48.) was used to predict the stability behavior of colloidal silica dispersed in ionic micellar solutions.  Comparisons are drawn between the stability ratio analysis and photographic analysis and ultraviolet-visible (UV-VIS) light spectroscopy results for the stability of dispersions of 0.5 μm colloidal silica particles in solutions of C₁₄TAB and SDS at varying concentrations.