Thermodynamics of Micellization of SDS in the Presence of Promethazine Hydrochloride and Ethanol Medium

Micellization of sodium dodecyl sulphate using Conductometric titration technique was employed in this work. The specific conductivity versus surfactant concentration plots were analyzed using Boltzman sigmoid approach for the determination of the critical micelles concentration (CMC) of the SDS in absence and presence of PMZ at different temperature. The thermodynamic parameters of micellization, such as change in the free Gibbs energy (ΔG_m^0), enthalpy (ΔH_m^0), entropy ((ΔS_m^0)), Gibbs energy of transfer (ΔG_(m.tr)^0), enthalpy transfer (ΔH_(m.tr)^0)and entropy transfer ((ΔS_(m.tr)^0)) were obtained from the CMC measurement in these study, using the phase separation model of micellization. SDS micelles were micellized and stabilized earlier when PMZ concentrations rose from 0.1 mM to 0.25 mM in aqueous. The obtained values of (ΔG_m^0 were generally negative and varied slightly with temperature which indicates the spontaneous aggregation process. The magnitude of enthalpy transfer (ΔH_(m.tr)^0 was positive in PMZ/H2O which denote that the transfer of hydrophobic portion from aqueous SDS medium to PMZ/SDS system in water are endothermic in nature. In the presence of PMZ, the reduced CMC values strongly suggest favorable, early aggregation and stabilization of SDS micelles. Overall, SDS micellization is entropically regulated in the presence of PMZ. Negative ΔG_m^0 values for the micellization of SDS in water and in the presence of varying amounts of PMZ and ethanol account for the process spontaneity at all temperature.