Solubilization of Amphiphilic Hemicyanine Dyes by a Cationic Surfactant, Cetyltrimethylammonium Bromide

The solubilization of amphiphilic hemicyanine dyes by the micelles of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was studied as a function of surfactant concentration above the critical micelle concentration (CMC). The micelle-water partition coefficient, Kx, and the standard free energy of solubilization, DeltaG0, of these dyes in CTAB micelles was determined at 25.0°C by a differential spectroscopic method. The CMCs of CTAB in the presence of small amounts of these dyes were determined by a conductivity method at 25.0°C. The values of Kx and DeltaG0 for all six dyes were determined by an improved method that incorporates both conductance and differential absorbance data.