The effect of alcohols on the size of water-in oil microemulsion droplets

We have investigated the effect of adding alcohols on the size of the AOT/n-decane/water microemulsion droplets. Dynamic light scattering is used to measure the size of the water-in-oil microemulsion droplets. The effects of concentration on the measured apparent hydrodynamics radius are carefully corrected to obtain the actual size of the microemulsion droplets. It is found that the measured hydrodynamics radius of the microemulsion droplets increases with increased amounts of ethanol added in the sample. As for adding n-butanol, the measured hydrodynamics radius of the microemulsion droplets roughly remains the same in the investigated range. For adding long-chain alcohols, such as n-heptanol, the measured hydrodynamic radius of the microemulsion droplets decreases with increased amounts of alcohol. These findings can be explained by considering how the alcohols are partitioned in the aqueous phase, the oil phase, and the surfactant layer.