Electrochemical behavior of cationic-anionic surfactant solutions by cyclic voltammetry

The electrochemical behavior of cationic tetradecyltrimethylammonium bromide (TTABr), anionic sodium dodecylsulfate (SDS), cationic-anionic (catanionic) mixed surfactant and self-assembled solutions at Pt wire electrode has been studied by cyclic voltammetry (CV). On the basis of the cyclic voltammograms and determining the self-assembled structures by using freeze-fracture transmission electron microscopy (FF-TEM), the mechanisms of the electrochemical reactions near the electrode for the two surfactant self-assembled solutions, i.e., micelles and vesicles, are presented. When mixing TTABr and SDS, at the right mixing ratio of TTABr:SDS, vesicles are established spontaneously. The redox behavior of two vesicle-phase solutions at a constant total concentration of 25 mmol center dot L-1 with the ratios of TTABr:SDS 9.35:0.65 of positive charges of bilayer membranes and 1.25:8.75 of negative charges of bilayer membranes are investigated by cyclic voltammetry. These cyclic voltammograms of vesicles with different charges are compared with those of 100 mmol center dot L-1 TTABr and 100 mmol center dot L-1 SDS micelle solutions. This CV study on surfactant self-assembled solutions should open up a new method of study in surfactant science.