Stabilization of oil-in-water emulsions by non-ionic detergents: properties of synthetic detergents at anisole- and chlorobenzene-water surfaces

Abstract

As part of an investigation into the mechanisms of stabilization of emulsions, the interfacial activity of three synthetic non-ionic detergents, CH2·[CH2]15·[O·CH2·CH2·]xOH, with x = 3, 6 and 9, at the anisole-water and chlorobenzene-water interface has been determined by measurement of interfacial tension. Surface pressure (π)-area (A) relations have been derived. The films are more expanded than at the air-water interface and an equation of the form (π- πR)A = xkT fits the results. It is suggested tentatively that πR, which is in most cases positive, and which increases with polyoxyethylene chain length, arises from the interaction between the ethylene oxide chains as they approach closely. The apparent critical micelle concentrations determined from the interfacial tension-concentration curves are higher than the true critical micelle concentrations obtained at the air-water interface.