Herein, we report the surface properties and mixed micellization of cationic gemini surfactants (butanediyl-1,4-bis(dimethylcetylammonium bromide), pentanediyl-1,5-bis(dimethylcetylammonium bromide), and hexanediyl-1,6-bis(dimethylcetylammonium bromide), respectively referred to as 16-4-16, 16-5-16, and 16-6-16) in the presence of different mole fractions of ethyleneamines (ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine) at 303 K. The surface properties (critical micelle concentration (CMC), C 20 (surfactant concentration required to reduce the surface tension of the solvent by 20 mN • m -1 ), Γ max (maximum surface excess), A min (minimum surface area per molecule), and interaction parameter β (for mixed monolayer formation at the aqueous solution/air interface (β σ ) and for mixed micelle formation in aqueous medium (β m )) are reported. A synergistic effect has been observed in all instances that were found to be correlated with the chain length of ethyleneamines. The CMC values of 16-s-16 decreased with increasing amine concentrations, and the extent of the effect followed the sequence: tetraethylenepentamine > triethylenetetramine > diethylenetriamine > ethylenediamine and 16-6-16 > 16-5-16 > 16-4-16. The standard Gibbs energies of adsorption (∆G ads 0 ) and the excess free energies of micellization (∆G ex ) of 16-s-16 with the amines were also evaluated.

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Due to the potential use of amines as co-surfactants in microemulsions, the effect of adding alkylamines (C 4 -C 8 NH 2 ) on the aggregation properties of cationic gemini surfactants [pentanediyl-1, 5-bis(dimethylcetylammonium bromide) and hexanediyl-1, 6-bis(dimethylcetylammonium bromide), referred to as 16-5-16 and 16-6-16 compounds] has been studied using tensiometry at 303 K. Data on critical micelle concentration (CMC), the surface properties C 20 (the surfactant concentration required to reduce the surface tension by 20 mN/m), U max (maximum surface excess), A min (minimum surface area per molecule) evaluated from the surface tension versus surfactant concentration plot, the interaction parameters b r (for mixed monolayer formation at the aqueous solution/air interface), and b m (for mixed micelle formation in aqueous medium) are reported. A synergistic interaction was observed both in the micelle as well as at interface, as evident from interaction parameters. Theoretical models of Clint, Rubingh and Rosen were used to explain and compare the results. More synergistic interaction was observed in 16-5-16 as compared to 16-6-16. The CMC values of 16-s-16 (s = 5, 6) decreased with increasing amine concentrations and the extent of the effect followed the sequence: octylamine [ heptylamine [ hexylamine [ pentylamine [ butylamine.

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Alcohols are very important additives and played a measure role as co-surfactants in various industrial and research applications. While, Gemini surfactants are mainly used as effective emulsifiers, antifoaming agents, bactericidal agents, coating agents and corrosion inhibitors etc.  Therefore, it is important to study about the variations in alkanol concentrations which affects the aggregation number and other related parameters. Surface properties of gemini surfactant butanediyl-1,4-bis(dimethyldodecylammonium bromide) (12-4-12) has been studied by using fluorescence method. This method has been used to calculate the aggregation number (Nagg) and the other related parameters like dielectric constant (D), Stern Volmer binding constant (KSV) of mixed system. This method is also very important for the calculation of the micropolarity of the mixed system (gemini/alcohol). The micropolarity has been obtained with the help of the ratio of intensity of peaks (I1/I3) of the pyrene fluorescence emission spectrum. Cetylpridinium chloride and pyrene were used as quencher and probe, respectively. Keywords: Gemini surfactant, special alcohols, aggregation number, micropolarity