Light Scattering Study On The Second Virial Coefficient And Interaction Of AOT Reverse Micelles

The light scattering measurements for the microemulsions of AOT/water/ isooctane with the molar ratio of water to AOT being 40 and of AOT/water/toluene with the molar ratio of water to AOT being 12 at a series of temperatures have been carried out to obtain the molecular weights, the aggregation numbers, and the second Virial coefficients of the droplets in the microemulsions at different temperatures. The experimental results were used to explore the interactions between the droplets. It was found that for the system of AOT/water/isooctane, the second Virial coefficient decreases as the temperature increases, indicating that the enegy or the enthalpy of the penetration of the hydrophobic chains between two microemulsion droplets is positive and the penetration is driven by the entropy only. However for the system of AOT/ water/toluene, the second Virial coefficient increases with the temperature, indicating that the enegy or the enthalpy of the penetration is negative and the penetration is driven by the enthalpy. The eperimental results are in agreememt with that from measurements of heat of dilution for the same systemes.The scattering light intensities of the reverse micelle solutions of AOT/ isooctane and AOT/toluene at different concentrations and temperatures were also measured to obtain the critical micelle concentrations of AOT, the molecular weights, the aggregation numbers and the second virial coefficients of the aggregates at different temperatures. The experimental results showed that the interactions between the micelle droplets are weaker than that in the microemulsion systems.