New Force Field Parameters for the Sodium Dodecyl Sulfate and Alpha Olefin Sulfonate Anionic Surfactants

Molecular dynamics simulations were carried out to obtain new force field parameters of two most commonly used anionic surfactants: sodium dodecyl sulfate and alpha olefin sulfonate. The present united atom models, of those surfactants, fail to reproduce one of the most important thermodynamic properties, the surface tension. Therefore, by scaling the Lennard-Jones parameters, the potential well (ϵ) and the length (σ), we were able to fit the experimental data. The correct micelle structure of the surfactants was also captured with the new set of parameters. The new proposed united atom models of both surfactants were tested with two different water models, TIP4P/ϵ and SPC/E, and good agreement with actual experiments was found.