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The surface adsorption and micelle formation of the mixed aqueous solutions of fluorocarbon and hydrocarbon surfactants: II. Sodium perfluorooctanoate‐sodium decylsulfate system
Author(s) -
GuoXi Zhao,
BuYao Zhu,
YaPing Zhou,
Li Shi
Publication year - 1984
Publication title -
acta chimica sinica english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 0256-7660
DOI - 10.1002/cjoc.19840020205
Subject(s) - chemistry , adsorption , aqueous solution , heptane , micelle , pulmonary surfactant , hydrocarbon , surface tension , critical micelle concentration , gibbs isotherm , fluorocarbon , thermodynamics of micellization , inorganic chemistry , sodium , mole fraction , organic chemistry , thermodynamics , biochemistry , physics
The adsorption and micellar behavior of the mixed solutions of sodium perfluorooctanoate (7CFNa) and sodium decylsulfate (C 10 SNa) have been studied at constant ion strength of 0.1 m . The adsorption was calculated from the surface (and interfacial) tension‐concentration curves by applying Gibbs equation. It was found that the cmc's of 7CFNa and C 10 SNa are of nearly the same value (1.66 × 10 −2 m and 1.45 × 10 −2 m, respectively), but γ cmc of 7CFNa solution is ∼23 mNm −1 , which is much lower than that of C 10 SNa solution. This implies that 7CFNa would have a much higher surface activity than C 10 SNa and be adsorbed preferentially; for instance, 7CFNa has a surface mole fraction of about 0.8 in the saturated adsorption layer of the 1:1 mixed solution. The mole fractions of 7CFNa at the surface are always greater than those in the bulk solutions. The adsorption at the n ‐ heptane‐aqueous solution interface is quite different from that at the air‐solution surface. Here C 10 SNa is preferentially adsorbed owing to “Mutual phobicity” between the HC‐chain of n ‐heptane and the FC‐chain of 7CFNa at the interface. All the cmc's obtained from the γ‐log m relations of 7CFNa (or C 10 SNa) in the mixed solutions have nearly the same value and the cmc‐ x curves show a positive deviation from the ideal case. This further indicates that in the mixed solutions of fluorocarbon and hydrocarbon surfactants no completely miscible micelle but essentially the individual micelle of each surfactant exist due to the “Mutual phobicity” between FC‐ and HC‐chain in the micellization process.