The phase behavior of supercritical CO2/ClCF2CF2CF2CF2CF2CF2OCF2CF2SO3K (F-53B)/alcohols/water/was studied in detail using a high-pressure variable-volume view cell. The results showed that F-53B could form reverse microemulsions in the presence of water and alcohols from ethanol to n-octyl alcohol. A significant amount of water could be solubilized at easily accessible conditions. The efficiency of the alcohols to enhance formation of the microemulsions was in the order: n-pentanol approximate to n-butanol > n-hexanol > n-propanol approximate to n-heptanol > octyl alcohol > ethanol. The solvatochromic probe studies further proved the existence of water domains in the supercritical CO2-based microemulsions. The microemulsions may have potential applications because the surfactant is relatively cheap and simple in structure. and the reverse microemulsions can be formed at mild conditions. (C) 2004 Elsevier B.V. All rights reserved.