Computer Simulations of Surfactant Mixtures at the Liquid/Liquid Interface

Abstract

We performed molecular dynamics simulations on monolayers of surfactant mixtures at the water/carbon tetrachloride interface. The mixture was composed of sodium dodecyl sulfate (SDS) anionic surfactants and molecules that were chosen to be identical to SDS except that the charges were different in order to make them nonionic. Simulations were conducted for different concentrations of the monolayer mixture; i.e., at a fixed surface area we kept the number of SDS molecules constant while the number of the nonionic molecules was increased. Simulations of different SDS/nonionic mixtures show that the location of the surfactants in the interface is determined by the interaction and the charge distribution of the molecules. We also observe that the structure of the two different surfactants in the monolayer is different and is affected by the concentration of the mixture. For a particular SDS/nonionic mixture, the results indicate that the tails of the SDS molecules are less ordered than the tails of the nonion...