Abstract
The surface and micellar properties of cationic gemini surfactant butanediyl-1, 4-bis(dimethyldodecylammonium bromide), referred to as C
12
-C
4
-C
12
, has been studied in pure aqueous solutions and in the presence of alcohols (butanol (C
4
OH), pentanol (C
5
OH), hexanol (C
6
OH)), and the corresponding amines (butylamine (C
4
NH
2
), pentylamine (C
5
NH
2
), hexylamine (C
6
NH
2
)) by surface tension measurements at 303 K. Parameters such as critical micelle concentration (CMC), C
20
(the surfactant concentration required to reduce the surface tension of solvent by 20 mN m
−1
), the ratio of C
20
and CMC, Γ
max
(maximum surface excess concentration at the air/solution interface), and A
min
(minimum area per surfactant molecule) were evaluated. The CMC value of the gemini decreased with increasing concentration of additives. Mixed micelles were formed in each case and the CMC values of the mixtures were used to compute interaction parameters for mixed micelle formation in aqueous medium (β
m
), interaction parameters for mixed monolayer formation at the solution/air interface (β
σ
), and activity coefficients (f
1
and f
2
). A synergistic interaction was observed both in the micelle as well as at the interface, as evident from the interaction parameters. Free energies of micellization (
) and adsorption (
) were also calculated.