Lithium perfluorooctanoate

The first identification of intermediate -phase structures was by Luzzati et al. (84) from the measurements by Spegt and Skoulios (80-83) in anhydrous soap melts. It was not until the work of Kekicheff and others (72, 86-91) on sodium dodecyl sulfate (SDS)/water and on lithium perfluorooctanoate (LiPFO)/water (92) that... 

Fig. 6.43 Solubility of gas, expressed as moles of gas absorbed in 1000 g of water containing lithium perfluorooctanoate (shaded symbols) or sodium perfluorooc-tanoate (open symbols) and plotted as a function of surfactant concentration at 25°C. (From Ref. 220. Reproduced by permission of Academic Press.)...

Hoffmann et al. [55] examined the size and shape of micelles of LiPFO (lithium perfluorooctanoate) and DEAFN (diethylammonium perfluoronona-noate) by SANS. Mixtures of H2O and D2O were used as the solvent to increase the accuracy of SANS data by varying the contrast of the solvent. Spherical micelles were found in LiPFO solutions and spherical vesicles of various size in DEAFN solutions. 

The phase behavior of fluorinated surfactants and hydrocarbon surfactants is remarkably similar. Tiddy and co-workers [161-164] observed that ammonium perfluorooctanoate and lithium perfluorooctanoate, like hydrocarbon surfactants, form a hexagonal phase, a lamellar phase, and an intermediate phase. A reversed hexagonal structure originally postulated for the intermediate phase [163,164] was found to be inconsistent with F-NMR observations, and an alternative lamellar structure was proposed [165]. 

Hoffmann et al. [221,222] measured SANS of lithium perfluorooctanoate, diethylammonium perfluorononanoate, and tetraethylammonium perfluorooc-tanesulfonate micelles in D2O or in mixtures of D2O and H2O. The radii, micelle concentrations, and aggregation numbers were calculated. 

The volume change upon micellization reported for lithium perfluorononanoate by La Mesa and Sesta [85], AV = 18 2 mL/mol, corresponds to the value of 20 mL/mol estimated by Sugihara and Mukerjee for sodium perfluorooctanoate [135]. However, the value of 14.2 mL/mol reported by Johnson and Olofsson [132] for lithium perfluorononanoate is considerably lower than the value obtained by La Mesa and Sesta. The V, / = 21.5 1 mL/mol value estimated for perfluorooctanoic acid [88] is higher than that of its sodium salt and ... 

The pseudophase model (see Section 6.2) for micellar solutions makes it possible to establish a partitioning coefficient for the partitioning of the solubilizate between the aqueous solution and the micellar pseudophase. Treiner et al. [206-208] studied partitioning of alcohols and phenol in an aqueous solution of a fluorinated surfactant or of mixed anionic hydrocarbon and fluorocarbon surfactants. The fluorinated surfactants used in their studies were potassium or sodium perfluorooctanoate and lithium perfluorooctanesulfonate. 

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