Micellization and Thermodynamic Properties of Cationic Surfactant Cetyltrimethylammonium Bromide in non-Aqueous Mixture of Lauric Acid

Abstract

In this work, the multi technique approach has been utilized to study the intermolecular interactions in lauric acid with the cationic surfactant cetyltrimethylammonium bromide in non aqueous media. The pseudo-phase separation model was used for the calculation of various thermodynamic parameters like standard free energy, ΔGomic, enthalpy, ΔHomic, and entropy, ΔSomic, of micelle formation. The interfacial properties (the maximum surface excess at the air/solvent interface, Γmax, the minimum area per surfactant molecule at air/solvent interface, Amin) of mixed system were calculated by using the Gibbs adsorption isotherm. The density data were applied to calculate the apparent molar volumes at infinite dilution, Vϕo, apparent molar volumes at the critical micelle concentration, Vϕcmc, and apparent molar volumes upon micellization, ΔVϕm, at 298.15, 303.15, 308.15 and 313.15 K. The 1H NMR analysis suggested the intermolecular interaction especially in the hydrophilic head and interface region of CTAB with regard to shifting of proton signals.