Micellization and interfacial properties of cationic gemini surfactant (12-4-12) in the presence of additives in aqueous electrolyte solution: A tensiometric study

The critical micelle concentration (CMC) of cationic gemini surfactant butanediy1-1, 4-bis(dimethyldodecyl-ammonium bromide) with additives (primary linear alcohols (butanol, pentanol, hexanol) and primary linear amines (butylamine, pentylamine, hexylamine)) in presence of inorganic salt potassium nitrate is measured by surface tension measurements at 303 K in the present study. The CMC value of the gemini decreased with increasing concentration of additives and the extent of the effect observed was in the order: C6OH > C5OH > C4OH; C(6)NH2 > C5NH2 > C4NH2. The surfactant concentration required to reduce the surface tension of solvent by 20 mN m(-1), C-20, ratio of C-20 and CMC, maximum surface excess concentration at the air/solution interface, Gamma(max), and minimum area per surfactant molecule, A(min), were evaluated. The interaction parameters beta(sigma) (for mixed monolayer formation at the solution/air interface), beta(m) (for mixed micelle formation in aqueous medium) and f(1)(m), f(2)(m) (activity coefficients) were also reported. As evident from interaction parameters, a synergistic interaction was observed both in the micelle as well as at the interface. Rubingh and Rosen models were used to evaluate the interaction parameters for the mixed micelles and at mixed monolayer, respectively. The Delta G(m)(0), standard free energy of micellization, and Delta G(ads)(0), free energy of adsorption, were also calculated. (C) 2013 Elsevier B.V. All rights reserved.