Solubilization of cationic hemicyanine dyes in anionic surfactant micelles: A partitioning study

Cationic hemicyanine dyes of the 1-methyl-4-(4-(di-n-alkylamino)-styryl) py ridinium betain type (alkyl group = methyl to butyl) have been investigated by differential spectroscopy in order to ascertain their solubilization in aqueous micellar solution of sodium dodecylbenzene sulfonate (SDBS). The d ifferential absorption spectra were recorded as a function of surfactant co ncentration at 25.0 degrees C. Thermodynamic parameters were calculated fro m partition coefficient data. The results show that cationic hemicyanine dy es are solubilized at the micellar surface, indicating an electrostatic int eraction between dyes and surfactant micelles.