ABSTRACT
Surfactants adsorb onto fluid interfaces, where they reduce the surface tension. They are used as additives to regulate the surface tensions between immiscible fluids in a wide variety of applications. The fundamental understanding of dy namic surface tension in single surfactant systems is well developed in terms of the surfactant mass transfer and the thermodynamic relationship between the sur face concentration and the surface tension (as reviewed in Ref. 1). However, in most applications, surfactants are added as mixtures. These mixtures often have desirable properties caused by interactions among the components that are not achieved by a single surfactant. For example, the phenomenon of synergistic surface tension reduction is well documented; when two surfactants interact attrac tively, the net amount of surfactant adsorbed at the interface of the mixture is greater than the sum of the surface concentrations for the two components separately. As a result, the surface tension is strongly reduced (see, for example, Ref. 2).
