Water effect in the reverse micellar formation of docusate sodium. A coarse-grained molecular dynamics approach

Improving understanding and characterization of complex fluid systems are crucial tasks of integral product and process design. Of particular interest is the development of enhanced surfactants for industrial and household applications. In this work, a coarse-grained molecular model is developed to study docusate sodium-water-cyclohexane microemulsion systems. Most of the model parameters are taken from a corresponding states treatment of the statistical associating fluid theory-γ-Mie equation of state, overcoming time-consuming simulations. A good agreement is found between model predictions and experimental data, including the phase boundary and reverse micellar aggregation numbers. The effect of water over the morphology of single reverse micelles was studied over the water:surfactant molar ratio range 1 – 14, where a predominant spherical shape was obtained with an average shape anisotropy value of 0.003. The gained molecular insights would be further exploited for the design of more efficient, effective and non-toxic surfactants.