Solubilization of a water-insoluble dye: A light-scattering study

Abstract

In aqueous solutions of ionic surfactants above critical micelle concentration (CMC) spherical micelles form. Adding salt causes screening of their charges. This may result in one-dimensional growth, leading to micelles with wormlike shape. Dye-containing micelles in the presence of salt can adopt a similar structure. — The static light-scattering technique was used to get information about the structure of dye-containing micelles of the cationic surfactant tetradecyl-trimethylammoniumbromide (TTAB). The following results were obtained: At the same salt concentration dye-containing micelles are much larger than those without solubilized dye. Obviously, dye and salt act synergistically on the growth of wormlike micelles. — The flexibility of the dye-containing wormlike micelles is higher when the salt concentration is increased. This, in turn, can be explained by the screening of the charges, which decreases chain-stiffness of the micellear aggregates.