Solvation Thermodynamic Parameters for Alkyl Benzyl Dimethyl Ammonium Chloride and Cetyl Trimethyl Ammonium Chloride Surfactants in Water and Alcoholic-Water Solvents

The conductivity of both alkyl benzyl dimethyl ammonium chloride (BAC) and cetyl trimethyl ammonium chloride (CTAC) surfactants in water and in alcoholic-water mixed solvents (methanol, ethanol, and glycerol) with different mole fractions of alcohols has been measured at temperatures (298.15, 303.15, 308.15, and 313.15 K). From the measured data of conductivity and surface tension, the critical micelle concentration (cmc) of both BAC and CTAC was determined. The cmc was found to increase as the temperature and alcohol mole fraction increased. From the conductivity values before the cmc, the association constant (K-a) of both BAC and CTAC was estimated using Shedlovsky equation. The values of (Delta G, Delta H, and Delta S) of the micellization and association processes were estimated. The association constant of the BAC and CTAC was found to decrease as the temperature and alcohol percentages increase. It was found that the association process is a spontaneous process. At 298.15 K, the density and refractive index of BAC and CTAC in water and in alcoholic-water mixed solvents (methanol, ethanol, and glycerol) with different mole fractions of alcohols have been measured. From the density values, the molal volume of both BAC and CTAC was determined and discussed. Also, from the refractive index values, the molar refraction and polarizability of the surfactants under study were estimated and discussed.