Phase behavior, structural effects, and volumetric and transport properties in nonaqueous microemulsions

We report here results concerning nonaqueous microemulsions containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT)+ hexane + nonaqueous polar component, i.e., ethyleneglycol/2-pynolidinone/ glycerol/methanol, over a wide range of volume fraction (phi) of dispersed phase at 30 degrees C. The influence of such nonaqueous systems on conductivity, dynamic viscosity, density, and ultrasonic velocity have been investigated. Electrical conductivity (sigma) and viscosity (eta) data show the existence of a percolation threshold. An excellent agreement between the (sigma/phi)(expt) and (sigma/phi)(calc) calculated from the prediction of the droplet charge fluctuation model has been observed. The aggregation number (n), core radius (r(n)), and surface number density of the surfactant molecules at the interface (alpha(s)) have also been computed. Droplet size in the case of the AOT + hexane + methanol system primarily depends on the molar ratio omega, according to r(n)=0.545 (+/- 0.021) + 0.366(+/- 0.006)omega. The phase behavior showing the realm of existence of microemulsion for the systems AOT + hexane + ethyleneglycol/methanol has been delineated at 30 degrees C.