Investigation on the solubilization of organic dyes and micro-polarity in AOT water-in-CO 2 microemulsions with fluorinated co-surfactant by using UV-Vis spectroscopy

Abstract

It was found that organic dyes such as thymol blue, dimidium bromide and methyl orange which are not soluble in pure supercritical CO 2, could be conveniently solubilized in AOT water-in-CO 2 reverse microemulsions with 2,2,3,3,4,4,5,5-octafluoro-1-pentanol as co-surfactant. The solubilities of these organic dyes in the microemulsions were measured successfully by using a UV-Vis spectroscopy method newly established in our laboratory; besides that, for a given temperature, a critical micelle pressure (CMP) at which formation of AOT water-in-CO 2 reverse micelles starts, was determined in term of the effect of pressure on the absorption intensity of the organic dyes in the microemulsions. Furthermore, the micro-polarity environment of the AOT water-in-CO 2 reverse microemulsions was investigated systematically according to the shift of solvatochromic probes such as methyl orange and dimidium bromide with varying water content by using UV-Vis spectroscopy.