6533b870fe1ef96bd12d03fa

RESEARCH PRODUCT

Demixing of Mixed Micelles. Thermodynamics of Sodium Perfluorooctanoate−Sodium Dodecanoate Mixtures in Water

subject

description

Conductivity, density, heat capacity, enthalpy of dilution, and osmotic coefficient measurements of water−sodium perfluorooctanoate (NaPFO)−sodium dodecanoate systems were carried out as functions of the surfactants' total molality (mt) at different mole fractions (XNaPFO). From conductivity data, the critical micelle concentration (cmc) and the degree of ionization (β) of the micelles were derived. The cmc's of the micelles are higher than those of the pure surfactants while β depends linearly on XNaPFO. At a given mole fraction, the apparent molar volume (VΦ) and heat capacity (CΦ) of the mixture increases and decreases monotonically with mt, respectively. From data in the premicellar region, the standard (infinite dilution) partial molar properties (Yo) of the mixtures were calculated for both volume and heat capacity. Yo depends linearly on XNaPFO according to the ideal behavior. From data in the postmicellar region, the excess properties (Yexc) for the mixed micelles formation from pure micelles were...