Ellipsometry Studies of Interfacial Film Formation in Emulsion Systems

Abstract

The possibility of using in situ ellipsometry for studies of the formation of interfacial films in emulsion systems was investigated. It was found that ellipsometry studies on dilute emulsions can provide information on the adsorption kinetics, the adsorbed layer structure, and the mechanisms of formation of the adsorbed layer. At high electrolyte concentrations, the adsorption from a model o/w emulsion stabilized by egg lecithin was found to be more pronounced at hydrophilic and negatively charged silica than at hydrophobic methylated silica. Furthermore, the adsorbed layer thickness at both surfaces is smaller than the average droplet size, corresponding to either small or "flattened" droplets or liposomes. The adsorbed layer thickness is smaller at methylated silica than at silica, presumably due to a larger degree of emulsion droplet or liposome spreading at this surface. In both cases, the adsorbed layer thickness is independent of the adsorbed amount, i.e., the adsorbed layer formation proceeds by attachment of droplets, which pack more densely with an increasing adsorbed amount.