Journal of Chemical Thermodynamics, Vol.74, 184-192, 2014
Mixed system of ionic liquid and non-ionic surfactants in aqueous media: Surface and thermodynamic properties
The mixed system of ionic liquid (IL) tetraethyl ammonium tetrafluoroborate [TEA(BF4)] and numerous ethylene oxide based non-ionic surfactants in aqueous media were studied using surface tension, viscosity and dynamic light scattering (DLS) measurements. Various surface properties like critical micelle concentration (cmc), maximum surface excess concentration (Gamma(max)), minimum surface area per surfactant molecule (A(min)), surface tension at the cmc (gamma(cmc)), adsorption efficiency (pC(20)), and effectiveness of surface tension reduction (pi(cmc)) as well as thermodynamic parameters of micellization have been determined. DLS and viscosity measurements revealed that the micellar growth was attributed to the bridged solvophilicity of the POE chain in surfactants at elevated temperatures. In most of the cases, the progression ensues from exothermic to endothermic with increase in temperature of the mixed system. Thermodynamic parameter indicates that the micelle formation process is enthalpy driven at low temperature and entropy driven at higher temperature. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords:Ionic liquid;Tetraethyl ammonium tetrafluoroborate [TEA(BF4)];Non-ionic surfactant;Surface tension;Thermodynamics parameters