SAC: Surface activity coefficient, a function to unveil surface and bulk’s ideal - non ideal behavior

Abstract

Abstract The quotient between the reduced surface pressure and the amphiphile mole fraction corresponds to the surface activity coefficient which is analogous to the bulk activity coefficient under the symmetric convention. This property indicates the ideal and non-ideal behavior of the bulk and surface phases. The main advantage of the construction followed in this work is that the contributions from the bulk and surface deviations from ideality can be separated into independent contributions. The non-ideality of the surface phase is not found in the volumetric phase. The natural logarithm of the surface activity coefficient as a function of the reduced surface pressure allows to identify different configurations of bulk and surface ideality or non-ideality. Binary systems showing ideal behavior in the surface and bulk phases, non-ideal behavior in the surface but ideal behavior in the bulk phase, ideal behavior in the surface and non-ideal behavior in the bulk phase, and systems exhibiting non-ideal behavior in both regions are analyzed and compared with experimental data and classified with the presented model..