Conductance Study of the Thermodynamics of Micellization of 1-Hexadecylpyridinium Bromide in Mixed Solvents Containing Dilute Electrolyte Solutions

The critical micelle concentration (CMC) of hexadecylpyridinium bromide (HDPB) is determined conductometrically in binary mixtures of water + cosolvent at various temperatures and at low concentrations of sodium bromide, ranging from 0 to 2.4 × 10-2 M. Dimethylsulfoxide (DMSO) and acetonitrile (AN) were used as cosolvents added to water. The ability of NaBr to lower the CMC of HDPB in water is inhibited by DMSO and AN. Thermodynamic parameters of micellization ΔHmº, ΔSmº, and ΔGmº are evaluated according to the pseudo-phase model. The contribution of DMSO and AN in the micellization process of HDPB in aqueous electrolyte solutions are discussed in terms of the observed thermodynamic properties