Thermodynamic Study of Temperature and Dimethyl Formamide on the Micellization of Hexadecyltrimethylammonium Bromide

The aggregation behavior of surfactants in aqueous–organic mixed solvents has been the subject of much attention in the past few years [1-3]. In this work, the effect of dimethyl formamide on the critical micelle concentration (CMC) of hexadecyltrimethylammonioum bromide (HTAB) have been investigated by conductometeric measurement method at T= (298.2, 308.2 and 318.2) k. The CMC values of HTAB were measured in pure water and water + dimethyl formamide mixtures containing 10, 20 and 30% dimethyl formamide.The thermodynamic properties such as the free energy change of micellization , the entropy change of micellization , and the enthalpy change of micellizaton have been obtained for the studied surfactant solutions with or without organic solvent by using the measured CMC data. The obtained results show that the CMC values increase with increasing temperature and dimethyl formamide concentration.