The effect of chemical structure upon the thermodynamics of micellization of model alkylarenesulphonates. Prediction of micellar properties with the Poisson‐Boltzmann model

Abstract

Abstract. This paper describes how the theory of the "dressed micelle", which is based on the nonlinear Poisson-Boltzmann equation, can be used to calculate a number of thermodynamic quantities for micellization of sodium p-alkylbenzenesulphonates. From the Gibbs energy of micellization, the enthalpy of micelle formation is calculated and compared with calorimetric enthalpies. A number of other thermodynamic quantities, such as the degree of counterion binding, the electrostatic surface potential of a micelle, and the entropy of micelle formation, have also been calculated as a function of temperature and surfactant structure and, where possible, compared with experimental data. In general, the calculated thermodynamic parameters obtained using the model show the same trend with respect to temperature and structure as the experimental quantities. The absolute values, however, differ from the experimental quantities. Finally a comparison is made between the Poisson-Boltzmann model, the phase-separation model and the mass-action model.