Potentiometric Study of Intermolecular Interactions in Cationic-Nonionic Mixed Surfactant Systems

摘要

The nature and thermodynamics of interactions of the cationic surfactant dodecyltri-methlammonium bromide (DTA) with the nonionic surfactant Triton X-100 (TX100) in mixtures are studied using the potentiometric method. We investigate the influence of temperature, the addition of KBr, and the concentrations of DTA and TX100 on the complex formation between free DTA cations and TX100 nonionic micelles in solution. Binding isotherms, distribution coefficients K_x, and stoichiometric equilibrium constants K_1 are determined from th experimental data. The standard free energy change (ΔG_1 deg), the standard enthalpy change (ΔH_1 deg) adn the standard entropy change (ΔS_1 deg) are calculated for transferring teh free DTA cation from the aqueous buld phase to the TX100 nonionic micelle phase. Our results support the assumption that hydrophobic interactions are the most important in this binding process.