Micellar solutions with added salt

Abstract

The spherical cell model is used to investigate the structural and thermodynamic properties of common micellar solutions with added salt. The model is analysed using Monte Carlo simulations, the classical Poisson-Boltzmann theory, and the modified Poisson-Boltzmann theory. It is seen that for monovalent systems the modified Poisson-Boltzmann theory can reproduce the Monte Carlo results accurately over a wide range of polyion and added salt concentrations. The structural predictions of the Poisson-Boltzmann theory on the other hand, deviate from the Monte Carlo values at higher concentrations although the predicted osmotic pressures are surprisingly good. For divalent systems the Poisson-Boltzmann theory is useful at low polyion and salt concentrations with the modified Poisson-Boltzmann thermodynamic results being generally closer to the simulations.