THERMODYNAMICS OF MICELLIZATION OF AEROSOL OT IN POLAR AND NONPOLAR-SOLVENTS - A CALORIMETRIC STUDY

The critical micelle concentration (cmc) and the thermodynamics of micellization of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in four polar solvents (water, ethylene glycol, propylene glycol, and formamide) and seven nonpolar solvents (hexane, heptane, octane, isooctane, decane, dioxane, and benzene) have been determined by spectrophotometry and calorimetry. Normal and reverse micelle formation processes have taken place in the two categories of solvents. The cmc values in all the solvents have been found to be on the order of m mol dm-3 with a systematic trend in alkanes. The polar solvent media as well as dioxane and benzene show positive enthalpies of micellization. The alkanes show a negative enthalpy of micellization, decane being an exception to this. The entropies of micellization of these two categories of solvents are also of opposite signs. A nice correlation between the enthalpy and entropy of micellization encompassing all the solvents has been observed.