EFFECT OF ELECTROLYTES ON THE MICELLIZATION OF IONIC SURFACTANTS IN NORMAL-ALKANOL-WATER MIXTURES

The effect of temperature on the CMC of sodium dodecyl sulfate and cetyltrimethylammonium bromide has been studied in n-alkanol-water mixtures at different temperatures. The CMC was found to decrease initially and increases further with rise in temperature. From the temperature dependence of CMC, various thermodynamic quantities have been computed in these solvent mixtures. The effect of univalent counterions on the CMC of both surfactants has been studied in n-butanol-water mixture. In the presence of alcohol the CMC was found to decrease with decrease in their crystallographic radii. The free energy of hydrophobic bond formation and the degree of dissociation of the micelles have been calculated from log CMC vs log counterion concentration plots. The results have been discussed in terms of increased hydrophobic effect at lower temperature, in the presence of electrolytes and the chain length of alcohols in the solvent mixtures. © 1979.