Complex formation study of hemicyanine dyes with sodium dodecyl sulfate by differential spectroscopy

Complex formation of hemicyanine dyes within anionic surfactant sodium dodecyl sulfate is investigated using differential absorbance method. Micelle–water partition coefficients are calculated as a ratio of the mole fractions of dye in corresponding phases. The thermodynamic parameters highlight the energy efficiency of the process. Conductometric study is utilized to show the depression in critical micelle concentration of sodium dodecyl sulfate caused by each dye. In contrast to sodium dodecyl benzene sulfonate, where pyridinium nitrogen forms highly stable complexes with aromatic moiety of the surfactant, the dye bound to SDS through salt-like electrostatic interaction. More hydrophobic dyes are more efficiently solubilized as compared to their less hydrophobic homologs.