REFRACTIVE-INDEX OF WATER-AOT-N-HEPTANE MICROEMULSIONS

Refractive index measurements on water/AOT/n-heptane microemulsions as a function of the volume fraction phi of the dispersed phase (water p lus AOT) and of the water/AOT molar ratio R have been performed at 25- degrees-C. The refractive index was found to vary monotonically with p hi without any change in rate during the crossover of the percolation threshold. Such a behavior suggested that, well above the percolation threshold, the water-AOT-n-heptane microemulsions are still formed by water-containing AOT reversed micelles dispersed in the oil phase. The analysis of the experimental data allowed an evaluation the fraction of the water molecules bonded to the AOT head group as a function of R .