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 (Γ_max) and minimum surface area per molecule (A_min) 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 β^m (the interaction parameter for mixed micelle formation in aqueous medium), β^σ (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.

Keywords:

• Alkylamines
• gemini surfactant
• mixed micelle
• synergism

R.M. is thankful to UGC for financial assistance.