COSURFACTANT CONCEPT

Experimental investigations on the action of cosurfactants are reported using atypical additives. Thus, benzene, cyclohexane, nitrobenzene, etc., were added to a W O microemulsion (H2O/AOT/i-C8H18) thereby considerably increasing the maximum amount of solubilized water at a specified temperature. This specially selected system revealed a particularly interesting insight into the mechanism of the cosurfactant action and made generalizations possible. An extension of the approximate thermodynamic treatment from a ternary (≙ microemulsion) to a pseudoternary (≙ microemulsion + additive) system has been considered. The conclusions derived from the theoretical treatment are in satisfactory agreement with the experimental findings, and predict a mutual interaction between surfactant and cosurfactant resulting in a variation of the interfacial activity of the surfactant. © 1979.