Dielectric spectroscopy of micelle hydration and dynamics in aqueous ionic surfactant solutions

Abstract

The dielec. relaxation of ionic surfactant solns. is discussed by comparing results for cationic (alkyltrimethylammonium halides, CnTAX) and anionic (sodium dodecylsulfate, SDS) model surfactants. A careful anal. of the spectra yields quant. information on the hydration of the formed micelles as well as on their size and on the surface diffusion of the bound counterions. The results are not only self-consistent but can be directly linked to data obtained with other methods. Whereas the surface of SDS micelles is strongly hydrophilic with adsorbed counterions generally sepd. by a layer of water mols., the surface of CnTAX micelles is essentially hydrophobic and bound halide ions are directly attached.