Micelle Formation and Phase Equilibria in a Water-Trifluoroethanol-Fluorocarbon Surfactant System.

The soln. behavior of the fluorinated surfactant tetraethylammonium perfluorooctane-sulfonate, PFOS, in water-trifluoroethanol, TFE, mixts. has been investigated by surface tension, elec. conductance, and PGSE (pulsed gradient spin-echo) NMR self-diffusion methods. Addn. of progressive amts. of TFE in the solvent has little influence on the crit. micellar concn., CMC. Conversely, self-diffusion, counterion binding, and the surface pressure at the CMC are significantly affected by added fluoroalkanol. The above effects have been explained in terms of the solvent viscosity, dielec. permittivity, and surface activity, resp. The complete phase behavior of the above system has been drawn, and the phase boundaries were detd. According to the above findings, added surfactant promotes the sepn. of the homogeneous solvent mixt. into two coexisting fluid phases. The obsd. behavior was rationalized on thermodn. grounds