The Interaction of Cationic Gemini Surfactant 1,4-Butanediyl-α,ω-bis(dimethylcetylammonium bromide) with Primary Linear Alkanols

Abstract

The critical micelle concentration (CMC) of cationic gemini surfactant 1,4-butanediyl-α, ω-bis(dimethylcetylammonium bromide; C₁₆-C₄-C₁₆) with and without additives (primary linear alcohols: butanol (C₄OH), pentanol (C₅OH), hexanol (C₆OH), heptanol (C₇OH), octanol (C₈OH)) is measured by surface tension measurements using a du Noüy tensiometer in aqueous solution at 303 K. The CMC of C₁₆-C₄-C₁₆ decreased with increasing alcohol concentration and the effect followed the order: C₈OH > C₇OH > C₆OH > C₅OH > C₄OH. The surfactant concentration required to reduce the surface tension of the solvent by 20 mN/m, C₂₀, 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_t (C_t is the total surfactant concentration) plots. Mixed micelles were formed 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 respective activity coefficients (f₁ and f₂). The standard Gibbs energy of adsorption was also evaluated. We observed synergism in C₁₆-C₄-C₁₆/alkanol systems at all concentration ratios.

Keywords:

• Alkanols
• gemini surfactant
• mixed micelles
• synergism

Acknowledgments

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