Molecular simulation of the morphology and viscosity of aqueous micellar solutions of sodium lauryl ether sulfate (SLEnS)

Abstract

Abstract In a recent contribution, we introduced a new approach for the quantitative prediction of the micellar morphology of aqueous solutions of ionic surfactants based on coarse-grained MARTINI-type simulations followed by reverse-mapped all-atom (AA) molecular dynamics (MD) ones, using as a model system sodium dodecyl sulfate. We make use of the same approach in the present work to study the micellar structure of aqueous solutions of sodium lauryl ether sulfate (SLEnS) with the chemical structure CH3(CH2)11(OCH2CH2) n OSO3Na with a fixed number n of ethoxyl (EO) groups per surfactant molecule (n = 1, 2, 3). These surfactants are used in a wide range of industrial applications, particularly in personal and home care products, but a quick literature survey proves that a systematic study of their microstructure, micellar morphology, and equilibrium transport properties is missing. Our simulations provide predictions for the mean aggregation number of such monodisperse SLEnS solutions which are found to be in very good agreement with experimental data already reported in the literature. They also show that for a given total surfactant concentration, SLEnS molecules with a smaller number n of EO groups form, on average, larger micelles. From the reverse-mapped AA MD simulations we also compute the zero shear rate viscosity of the solution whose value is found to increase as its total concentration in SLEnS molecules increases (for a given n) or as the number n of EO groups in the surfactant increases (for a given concentration).