INVESTIGATION OF COSOLVENT EFFECTS ON THE SOLVATION OF AOT REVERSE MICELLES IN SUPERCRITICAL ETHANE

We present spectroscopic evidence of the preferential solvation and pe netration of the cosolvents benzene and methylene chloride into the su rfactant tail regions of AOT reverse micelles in supercritical ethane. The micropolarities on both sides of the AOT surfactant interface wer e investigated using the UV-vis absorption probes phenol blue and meth yl orange. Phenol blue was identified to reside in the surfactant tail region of the AOT reverse micelles, and its wavelength of maximum abs orption remained sensitive to property changes in the ethane continuou s phase. Furthermore, the preferential penetration of cosolvents benze ne and methylene chloride was observed as evidenced by a synergistic e ffect (enhanced red shift) on the phenol blue absorption spectra over the experimental pressure range. Studies with the probe methyl orange, which resides in the reverse micelle core, further showed that, while the composition of benzene is enhanced in the surfactant tail region, benzene did not penetrate the reverse micelle core.