Effective charges of micellar species obtained from Brownian dynamics simulations and from an analytical transport theory

Abstract

We focus here on the effective charge of ionic micelles in aqueous solutions. First, we show that this quantity may be obtained by using an analytical transport theory based on the continuous solvent model to fit the experimental electrical conductivity of micellar solutions. In particular, we demonstrate the robustness of the fitting procedure on the example of real aqueous solutions of n-dodecyltrimethylammonium bromide and n-tetradecyltrimethylammonium chloride. Moreover, the approximate theoretical results are validated by a comparison to numerical simulations of Brownian dynamics. On the other hand, we propose to investigate the condensation properties of counterions on the micellar species by using Brownian dynamics. For that purpose, we have performed simulations of aqueous solutions that contain micellar species carrying their structural charge and the adequate number of counterions. We obtain a qualitative agreement between the fitted effective charges and the ones obtained by computing the mean number of bound counterions from numerical simulations.