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

Abstract

Herein we report the effect of chain length of alkyl amines on the critical micelle concentration (CMC) of cationic gemini surfactant butanediyl-α, ω-bis(dimethylcetylammonium bromide) (abbreviated as C16-C4-C16). The CMC of different mixtures has been measured by surface tension using a du Noüy tensiometer in aqueous solution at 303 K. 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 20 mN/m), ratio of C20 and CMC, maximum surface excess (Γmax) 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 βm (the interaction parameter for mixed micelle formation in aqueous medium), βσ (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 () was also evaluated.