13C NMR INVESTIGATION OF THE STRUCTURE OF ALKYLAMMONIUM CHLORIDE MICELLS IN AQUEOUS SOLUTIONS
Y. A. Mirgorod, E. B. Postnikov, N. A. Borshch
Keywords: 13С NMR, alkylammonium chlorides, structure of micelles in water, structural model of association
Pages: 1147-1154
Abstract
13C NMR chemical shifts are obtained for aqueous solutions of alkylammonium chlorides (С6-С9) in the region of the critical micelle concentration (CMC). A new method of processing 13C NMR experimental data for aqueous solutions of alkylammonium chlorides is developed to calculate the aggregation numbers N of micelles and the equilibrium constants K of the micelle formation within the law of mass action. With the use of these N and K values the standard Gibbs energy of the micelle formation and its increment of
-1.8 kJ/mol are found for the methylene group. A small increment confirms the hypothesis about the structure of micelles consisting of both contact and hydrated associates. The structural model of the association of alkylammonium chlorides in water, the effect of alkyl chain length on the CMC, the hydrophobic interaction, the formation of hydrate associates, and also a possible classification of surfactants based on this are discussed.
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