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    Aggregation and Thermodynamic Properties of Some Cationic Gemini Surfactants
    (Wiley, 2012) Akbas, Halide; Elemenli, Aylin; Boz, Mesut
    In this study, the gemini surfactants of the alkanediyl-alpha-omega-bis(alkyl dimethyl ammonium) dibromide type, on the one hand, with different alkyl groups containing m carbon atoms and an ethanediyl spacer, referred to as m-2-m (m = 10, 12 and 16) and, on the other hand, with n-C-16 alkyl groups and different spacers containing s carbon atoms, referred to as 16-s-16 (s = 2, 6, 10 and Ar (8)) have been synthesized, purified and characterized. The critical micelle concentration (CMC), micelle ionization degree (alpha) and Gibbs free energy of micellization (a dagger G (mic)) of these surfactants and the monomeric cationic surfactants DTAB and CTAB have been determined by means of electric conductivity measurements. In addition, the temperature dependence of the CMC was determined for the 10-2-10 gemini surfactant. The CMCs of the gemini surfactants are found to be much lower than those of the corresponding monomeric surfactants and the effect of the hydrophobic alkyl chain length is more important than that of the spacer. The CMC of 16-s-16 passes through a maximum of (or around) s = 6 and then decreases for s = 10. The presence of a maximum CMC is explained by the contribution of a change of conformation of the surfactant with increasing spacer chain length. The changes of alpha with s and m are found qualitatively similar to those found for CMC values. The values of a dagger G (mic) are more negative for the dimers than for the monomers and also change with an increasing spacer carbon number, as CMC values do. The thermodynamic parameters of micellization indicate that the micellization of 10-2-10 is enthalpy driven.
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    Interaction between cationic gemini surfactant and related single-chain surfactant in aqueous solutions
    (Elsevier, 2014) Akbas, Halide; Boz, Mesut; Elemenli, Aylin
    In this paper, the gemini surfactants of type alkanediyl-a-co-bis (alkyldimethylammonium) dibromide with different spacers containing s carbon atoms, referred to as 16-s-16 [C16H33(CH2)(2)N+(CH2)sN(+)(CH2)(2)C16H33.2Br-], (s=2, 6, 10 and Ar (8)) have been synthesized, purified and characterized in our laboratory. The interactions between geminis and their conventional monomeric surfactant hexadecyltrimethylammonium bromide (CTAB) have been studied using the conductivity and steady-state fluorescence quenching techniques at a certain micellar concentration range and certain temperature. Using the conductance data, the values of critical micelle concentrations (CMC) of the binary gemini-conventional mixtures having different compositions have been obtained. The micellar interaction parameters, (beta), were determined from the critical micelle concentration values using the approach of Rubingh's regular solution theory. Mixed systems were exhibited negative synergism due to positive beta values. The beta values were found as close to zero. This indicates that the mixed micelle formation is ideal for all studied mixtures. The micelle aggregation numbers (N-agg evaluated using steady-state fluorescence quenching at a total concentration of 2 mM for CTAB/16-s-16 (s= 2, 6, 10 and Ar (8)) systems. It was observed that contribution of conventional surfactants was always more than that of the geminis. Using the ratio of peak intensities, the micro-polarity, dielectric constant and binding constant (K-sv) of mixed systems were determined. (C) 2014 Elsevier B.V. All rights reserved.
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    Thermodynamic Study of the Interaction Between CI Reactive Red180 with Cationic Gemini Surfactant in Aqueous Solution
    (Asian Journal Of Chemistry, 2012) Akbas, Halide; Elemenli, Aylin; Batigoc, Cigdem; Boz, Mesut
    Interactions between Reactive Red 180 and cationic gemini surfactant solutions were investigated by means of electrical conductivity measurement:, at different temperatures ranging from 298.15 to 323.15 K. Gemini surfactant of the type N,N'-didecyl-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide referred as (10-2-10) was synthesized in our laboratory. It was observed that a decrease in the measured specific conductance of dye-gemini surfactant mixtures was caused by the formation of nonconducting or less conducting dye-surfactant associates. The aggregation of surfactant and dye takes place at a surfactant concentration far below the critical micelle concentration of the individual surfactant. The long-range electrostatic forces and short-range hydrophobic interactions are very important factors at the dye-surfactant aggregation in aqueous solutions. From conductivity data for dyes-gemini surfactant interaction such as micellar ionization degree, counterion binding, equilibrium constant and thermodynamic parameters of interaction were calculated. Thermodynamic parameters of interaction indicate that interaction of dye-(10-2-10) is enthalpy driven.