A molecular framework for modelling the surface tensions and surface excesses of dilute surfactant solutions

The straightforward molecular modelling of an aqueous surfactant system at concentrations below the critical micelle concentration (pre-cmc) conditions is unviable in terms of the presently available computational power. Considering a typical nonionic surfactant, a fully atomistic simulation that includes several micelles will require in excess of O(10) atom sites and several nanoseconds of real time. Here, we present an alternative that combines experimental information with simulations of a more modest size to understand the surface tension changes with composition and the structural behaviour of surfactants at the water-air interface. The crux of the matter is to express the surface tension as a function of the surfactant surface excess both in the experiments and in the simulations, allowing direct comparisons to be made. As a proof of concept a coarse-grained model of tetraethylene glycol monodecyl ether is considered at the air-