Effect of Alkylamine Chain Length on the Critical Micelle Concentration of Cationic Gemini Butanediyl-, -bis(dimethylcetylammonium bromide) Surfactant

Herein we report the effect of chain length of alkyl amines on the critical micelle concentration (CMC) of cationic gemini surfactant butanediyl-, -bis(dimethylcetylammonium bromide) (abbreviated as C16-C4-C16). The CMC of different mixtures has been measured by surface tension using a du Nouy tensiometer in aqueous solution at 303K. A synergistic effect was observed in all instances that were found to be correlated with chain length. It was found that the CMC of C16-C4-C16 decreased with increasing amine concentrations and the extent of effect followed the sequence: octylamine (C8NH2)heptylamine (C7NH2)hexylamine (C6NH2)pentylamine (C5NH2)butylamine (C4NH2). C20 (the surfactant concentration required to reduce the surface tension of the solvent by 20mN/m), ratio of C20 and CMC, maximum surface excess (max) and minimum surface area per molecule (Amin) were evaluated from surface tension versus log C (C is concentration) plots. Mixed micelles were formed with the gemini surfactant and the CMC values of the mixtures were used to compute m (the interaction parameter for mixed micelle formation in aqueous medium), sigma (the interaction parameter for mixed monolayer formation at the aqueous solution/air interface), and the activity coefficients (f1 and f2). The standard Gibbs energy of adsorption ([image omitted]) was also evaluated.