Phase behavior of novel fluorinated surfactants in supercritical carbon dioxide

A series of novel fluorinated analogues of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactants, the sodium salt of bis(3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol) sulfosuccinate (CF3(CF2) 3CH(2)CH(2)OOCCH(2)CH(SO3Na) COOCH2CH2(CF2)(3)CF3, di-HCF5), the sodium salt of bis( 2,2,3,4,4,4-hexafluoro-1-butanol) sulfosuccinate (CF3CFHCF2CH2OOCCH2CH(SO3Na) COOCH2CF2CFHCF3, di-HCF3), the sodium salt of bis(2,2,3,3-tetrafluoro-1-propanol) sulfosuccinate (HCF2CF2CH2OOCCH2CH(SO3Na)COOCH2CF2CF2H, di-HCF2), and the sodium salt of bis( 2,2,3,3,3-pentafluoro-1-propanol) sulfosuccinate (CF3CF2CH2OOCCH2CH(SO3Na) COOCH2CF2CF3, di-CF2), were synthesized and characterized by H-1 NMR, C-13 NMR, F-19 NMR and FT-IR spectroscopy, melting point, and elemental analysis. The pressure-temperature phase behavior for water-in-CO2 microemulsions stabilized by the four surfactants was tested and the P-T diagrams were determined. In the phase behavior experiments, pressures up to 35 MPa, temperatures up to 65 degrees C, and water-to-surfactant molar ratios (W-o) from 10 to 30 were tested. The cloud-point pressure in microemulsions stabilized by the four fluorinated surfactants increased with increasing temperature, and at a fixed temperature, the cloud-point pressure increased with increasing Wo. However, the cloud-point pressure was only slightly affected by an increase in the concentration of surfactant at a settled W-o. The phase behavior for water-in-CO2 microemulsions at different Cd(NO3)(2) concentrations in the aqueous phase with the surfactant di-HCF5 was also determined, which is useful for the formation of CdS nanoparticles in our future studies.