Surface force measurements in surfactant systems

Abstract

Measurement of the forces between solid surfaces immersed in a surfactant solutions can reveal a great deal about the molecular mechanisms behind adsorption and the effect that adsorption has on the forces between the surfaces. The interferometric surface force apparatus provides basic information such as the thickness of the adsorbed layer, the surface energy which is related to the adhesion between the surfaces and the apparent surface charge. This review illustrates the utility of the technique in three specific areas, i) the forces measured between mica surfaces in solutions of cationic surfactants, ii) the interaction between hydrophobic surfaces iii) forces in concentrated micellar solutions. Surface properties play an important role in the adsorption and the resulting surface forces measured in surfactant solutions. This is illustrated with recent measurements of the interaction between glass surfaces in CTAB solutions. These measurements were made with a recently developed surface force apparatus and the details of this device are presented and the advantages and limitations of the techniques discussed.