A molecular
modeling approach is presented with a focus on quantitative
predictions of the surface tension of aqueous surfactant solutions.
The approach combines classical Molecular Dynamics (MD) simulations
with a molecular-thermodynamic theory (MTT) [Y. J. Nikas, S. Puvvada, D. Blankschtein, Langmuir 1992, 8, 2680]. The MD component is used to calculate thermodynamic
and molecular parameters that are needed in the MTT model to determine
the surface tension isotherm. The MD/MTT approach provides the important
link between the surfactant bulk concentration, the experimental control
parameter, and the surfactant surface concentration, the MD control
parameter. We demonstrate the capability of the MD/MTT modeling approach
on nonionic alkyl polyethylene glycol surfactants at the air–water
interface and observe reasonable agreement of the predicted surface
tensions and the experimental surface tension data over a wide range
of surfactant concentrations below the critical micelle concentration.
Our modeling approach can be extended to ionic surfactants and their
mixtures with both ionic and nonionic surfactants at liquid–liquid
interfaces