Phase Behavior and Microemulsion Formation in Compressible Perfluorinated Monomer Oil and Water Mixtures

The phase behavior of mixtures of water, hexafluoropropylene (HFP), ammonium perfluorooctanoate (C8), fluorinated alcohol, and ammonium chloride is reported as a function of temperature, pressure, electrolyte concentration, and hydrophobicity of the surfactant blend. The addition of a short-chain alcohol, hexafluoro-2-methyl-2-propanol, to the water−HFP−C8 mixture promotes formation of microemulsion phases. Replacing the weak amphiphile with a medium-chain alcohol, for example, 2-perfluorobutyl-2-propanol or 2-perfluorohexyl-2-propanol, produces large liquid crystalline regions. Microemulsion formulations containing the fluorinated olefin in a near-critical state along with water, fluorinated surfactant, fluorinated alcohol, and salt follow the generic patterns of phase behavior common for conventional liquid mixtures as a function of experimental variables. Pressure has a strong effect on the phase behavior when one of the components is compressible.