Computer Simulations of Simple Oil/Water/Surfactants Systems / Computer Simulations of Simple Oil/Water/Surfactants Systems

Abstract

A simple oil/water/surfactant model is used to study the self-assembly of surfactants. The model contains only the most obvious elements: oil and water do not mix, and a surfactant is an amphiphilic molecule i.e. one side of the molecule likes oil but dislikes water, the other side likes water but dislikes oil. Computer simulations on large oil/water/surfactant systems show a surprisingly rich structural detail. Micelles are formed spontaneously in the water phase and a monolayer of surfactants is formed at the interface. Simulations on water/surfactant systems show that, depending on the shape of the head-group, disk-like or spherical micelles form at a particular surfactant concentration. The simulations yield a complete micellar size distribution function. Furthermore, we observe (equilibrium) dynamical processes such as the entering of single surfactants into micelles, single surfactants leaving micelles, the fusion of two micelles, and the slow breakdown of a micelle. We use our results to answer some controversial questions concerning the interactions that are essential for surfactant self-assembly.