Molecular Modeling and Simulations of Reverse Micelles

Abstract

The physiochemical properties of sodium di-2-ethylexylsulfoccinate (AOT) reverse micelles in isooctane have been examined since the 1940s by various spectroscopic methods including NMR, neutron scattering, X-ray scattering, quasi-elastic light scattering, and infrared spectroscopy. Several attempts have also been made to create a computational model of a reverse micelle. However, studies to date leave several important questions unanswered about the size and stability of reverse micelles. To address the questions that remain unanswered about the equilibrium size of a reverse micelle, we have conducted simulations of small AOT reverse micelles in isooctane at constant pressure and temperature. Results show that the shape of a reverse micelle depends on its size, i.e. its surface area to volume ratio, and that the density of water within the reverse micelle is density is significantly less than that of bulk water. These results must be considered when interpreting experimental studies about the equilibrium size of a reverse micelle. These studies lay a foundation for future studies of encapsulated polypeptides and reverse micelles made from surfactants other than AOT.