Micellization of cationic fluorocarbon and hydrocarbon surfactant mixture: Diethanolheptadecafluoro-2-undecanolmethylammonium chloride and dodecyltrimethylammonium chloride mixed system

To reveal the interaction between cationic fluorocarbon and cationic hydrocarbon surfactants, the mixed critical micelle concentration (CMC) of diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) and dodecyltrimethylammonium chloride (DTAC) in aqueous solution was determined using electrical conductivity measurements. An interaction parameter, β, of 1 was obtained by applying a regular solution theory (RST) to the mixed CMC. Further, partition coefficients of alcohols and pyrene-3-carboxaldehyde between the micelles and the aqueous phase were measured. All these data were interpretable using RST with β = 1, indicating a rather small repulsive interaction between DEFUMAC and DTAC compared with anionic fluorocarbon and hydrocarbon surfactant mixtures. This is due to the large different CMC values of the two surfactants.