Sodium perfluorodecanoate

Mukerjee and Handa [102-104] measured surface and interfacial tensions of dilute aqueous solutions of sodium perfluorobutyrate, sodium perfluorooc-tanoate, sodium perfluorodecanoate, sodium octyl sulfate, and sodium decyl sulfate at the air-water, hexane-water, and perfluorohexane-water interfaces. The surface and interfacial tension values, 7. were converted to interfacial pressures, n, where II = 70 — 7. The data obtained for dilute solutions indicated the affinity of the surfactant for the interface. 

Ikawa et al. [136] determined the critical solution temperature (Krafft point) and the critical solution pressure (Tanaka pressure) of sodium perfluorodecanoate in water. A phase diagram of sodium perfluorodecanoate versus pressure at 55°C is shown in Fig. 6.29. The curves of solubility versus pressure (aQb) and of cmc versus pressure (dQe) intersect at point Q, representing the Tanaka pressure. The phase diagram is divided into three regions solution of monomolecular species (S), the micellar solution (M), and the hydrated solid (C). The rapid decrease of solubility with increasing pressure (curve aQ) was attributed to the transfer of surfactant from micelles to the hydrated solid phase, which is accompanied by a large decrease in partial molar volume. 

Fig. 6.29 The phase diagram of sodium perfluorodecanoate concentration versus pressure at 55°C. M, S, and C denote the micellar, singly dispersed, and hydrated solid states, respectively Q, a triple point CSP, critical solution pressure. (From Ref. 136. Reproduced by permission of Plenum Publishing.)...

The Krafft point increases with increasing Tanaka pressure (Fig. 6.30). Sodium perfluorodecanoate (SPFDe) has the highest Krafft point of the surfactants included in Fig. 6.29 at any pressure applied at a constant temperature, such as 50°C. Hence, the range where micelles can exist is narrower for sodium perfluorodecanoate than for the other surfactants shown. 

Phase diagrams of the sodium perfluorodecanoate-sodium decyl sulfate-water system have been constructed from the dependence of solubility and cmc on temperature [202]. Two kinds of micelles were found a fluorocarbon-rich mixed micelle and a hydrocarbon-rich mixed micelle. 

Fig. 9.6 The 200-1800-cm Raman spectra of perfluorodecanoic acid (a) and its lithium (b), sodium (c), and ammonium (d) salts at 22°C. (From Ref. 72. Reproduced by permission of Academic Press, Inc.)...

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