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

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, Γmax, and minimum surface area per molecule, Amin, were evaluated from surface tension versus log Ct (Ct is the total surfactant concentration) plots. Mixed micelles were formed 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 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.