Effect of the Solvent on the Water Properties of Water/Oil Microemulsions.

Using IR spectroscopy and the UV-Vis absorption spectra of solubilized methyl orange (MO) as a probe, the properties of the water pool of some bis(2-ethylhexyl) sodium sulfosuccinate, (Aerosol OT) w/o microemulsions were investigated. The solvents used to prepare the micromulsions were cyclohexane, isooctane, and toluene. From IR water spectra, four different water species were detected. The relative amounts are found to depend on the water-to-surfactant molar ratio and also on the solvent. The water pool dielectric constants were determined from the position of the maximum of the MO absorption spectrum. The polarity increases as the water content solubilized in the microemulsions increases and also depends on the solvent. Copyright 1999 Academic Press.