Molecular dynamics study of salt influence on transport and structural properties of SDS micellar solutions

The results of all-atom molecular dynamics simulations of micellization in the salt-free sodium dodecyl sulphate (SDS) aqueous solution and in the solution with added 1:1 salt (sodium chloride) are reported. Micellar systems of different size are considered in order to study size effects. The influence of added salt on transport and structural properties of the SDS micellar solutions is investigated. The formation of a larger aggregate in the presence of the salt, compared to the salt-free surfactant solution, is observed. With the increase of the salt concentration the diffusion coefficients of coions, counterions, and water molecules decrease. The diffusivity of a premicellar aggregate demonstrates the non-linear dependence on the salt concentration, while the size of the aggregate remains constant. Along with transport properties, we also studied structural properties of the SDS micellar solution: aggregation numbers and sizes of surfactant aggregates, radial distributions of ions and various atoms.