Key words Reverse micelles
Structure of interfacial water
IR and 1H NMR spectroscopy of interfacial water
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract The structure of water solubilized by reverse aggregates of calcium bis(2-ethylhexyl) sulfosuccinate in deuterobenzene and toluene has been probed by Fourier transform-IR and 1H NMR spectroscopies. The νOD band of solubilized HOD (4% D2O in H2O) has been recorded as a function of the [water]/[surfactant] molar ratio, W/S. Curve fitting of this band showed the presence of a main peak at 2550 ± 13 cm−1 and a small one at 2405 ± 15 cm−1. As a function of increasing W/S, the frequency of the main peak decreases, its full width at half-height increases, and its area increases linearly. The 1H NMR chemical shift of solubilized H2O–D2O mixtures at W/S = 18.1 has been measured as a function of the deuterium content of the aqueous nanodroplet. These data were used to calculate the so-called “fractionation factor” of the aggregate-solubilized water, the value of which was found to be unity. The results of both techniques show that reverse aggregate-solubilized water, although different from bulk water, does not seem to coexist in “layers” of different degrees of structure, as suggested, for example by the two-state water-solubilization model.
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