Effect of organic counter-ions on the surface activity, micellar formation and dye solubilization behaviour of cationic surfactants

Abstract

The effect of eight organic counter-ions (aliphatic, both mono and dicarboxylates) on the surface and micellar behaviour of decyl and dodecyl ammonium carboxylates in aqueous solution has been examined by different physicochemical techniques such as surface tension, dye solubilzation, conductance viscosity and nuclear magnetic resonance. The effect of these counter-ions as observed from surface activity, and critical micelle concentrati on (CMC) is explained in terms of their condensation /penetration onto/into the micelles. The decrease in CMC and increase in counter-ion binding of

cationic surfactants is attributed to the increased hydrophobicity in alkyl chain of counter-ions. In the case of monocarboxylate counter-ions, CMC decreases significantly in the order: <i>n</i> -butyrate < propionate < acetate