Analysis of Reverse Micelles in AOT/Water/Isooctane using DLS and Molecular Dynamics


We use molecular dynamics (MD) and dynamic light scattering (DLS) measurements to analyze the basic reverse micellar structures in the AOT-water-isooctane system at different water to surfactant ratios at ambient temperature and pressure. We find good qualitative agreement for the morphology and behaviour of the reverse micelle structures molecular dynamics calculations and DLS measurements; however, the average values for the reverse micelle size distributions are systematically larger according to the DLS measurements. The later capture the average hydrodynamic size of the reverse micellar structures rather than the average distance from the outer hydrogen atoms in the AOT surfactant to the center of the structure, distance used in our MD simulations to estimate the size of the reverse micelles. This explains why the DLS measurements size predictions are systematically larger than MD-based estimations, but the trends are definitively in very good agreement. We studied the effect of zirconyl chloride on the micelle size distribution experimentally. We find that the salt has a significant effect on the size of the structures making them smaller as the concentration increases. We are in process of developing appropriate models to study these effects at the molecular level using MD methods. A first modeling attempt using a balanced model salt of Zr+4 and Cl- ions does not capture the size reduction observed experimentally with zirconyl chloride.

Cancun, Mexico