Micellization and interaction properties of aqueous solutions of mixed cationic and nonionic surfactants

The micellization process of binary surfactant mixtures containing cationic surfactants viz. dodecyl pyridinium halide (C12PyX; X = Cl, Br, I), tetradecyl pyridium bromide (C14PyBr), and hexadecyl pyridium halide (C16PyX; X = Cl, Br) and a nonionic surfactants viz. dodecyl nonapolyethylene glycol ether (C12E9), dodecyl decapolyethylene glycol ether (C12E10), dodecyl dodecapolyethylene glycol ether (C12E12), and dodecyl pentadecapolyethylene glycol ether (C12E15) in water at different mole fractions (0-1) were studied by surface tension method. The composition of mixed micelles and the interaction parameter, [3 evaluated from the CMC data obtained by surface tension for different systems using Rubingh's theory were discussed. Activity coefficient (f(1) and f(2)) of cationic surfactant (CnPyBr)/C12Em (n = 12, 14, 16 and m = 10, 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The stability factors for mixed micelles were also discussed by Maeda's approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant.