Thermodynamic and Interfacial Properties of Cationic Gemini Surfactant in the Presence of Alcohols

The micellar properties of the cationic Gemini surfactant ethanediyl-1,2-bis(dimethyldodecyl ammonium bromide), C12H25 center dot(CH3)(2)N+-(CH2)(2)-N+(CH3)(2)C(12)H(25 center dot)2Br(-) (12-2-12), with short chain alcohols have been studied by conductivity and surface tension measurements within the temperature range 293.15 K-313.15 K and alcohol percentage. The critical micelle concentration (CMC) of 12-2-12 solution, degree of ionization (alpha) and standard Gibbs free energy of micellization (Delta G(m)degrees), standard enthalpy of micellization (Delta H-m degrees) were calculated from conductivity and surface tension data. The experimental data show that the CMC values of cationic Gemini surfactants increased with addition of methanol, ethanol and n-propanol. The thermodynamic parameters (Delta G(m)degrees), (Delta H-m degrees) and (Delta S-m degrees) of micellization of 12-2-12 in alcohol were also calculated from the temperature dependence of the CMC values. CMC, (alpha), (Delta H-m degrees) and (Delta S-m degrees) increased linearly with increasing temperature. In the mixture of dimeric cationic surfactant (12-2-12) and alcohol solutions, the CMC values showed a slight increase with increasing alcohol concentration. CMC, maximum surface excess concentration at the solution/air interface, Gamma(max), minimum area per surfactant molecule, A(min), and the surface pressure at CMC, IICMC, values calculated from the surface tension measurements and thermodynamic parameters have been evaluated at same temperatures.