Polyoxyethylene-type Nonionic Surfactants Research Articles

Analysis of Distribution Model for Micellar Solubilization using Thermodynamics of Small Systems: Nonideality of Solubilization of Benzoic Acid Derivatives in Nonionic Surfactants

The distribution model for solubilization in micellar systems is investigated from the point of view of the thermodynamics of small systems. The description of solubilization in terms of distribution between two phases, the nonmicellar and micellar, provides a good approximation in many cases. Some consequences of treating the micellar phase as ideal and nonideal solutions are examined. It is shown that the solubilization of benzoic acid derivatives in polyoxyethylene-type nonionic surfactants shows serious deviations from ideality, which, however, can be incorporated quantitatively in the theory of regular solutions. The usual application of a Langmuir-type model, assuming binding to fixed sites in describing such nonidealities, is unwarranted.