Thermodynamics of comicellization of ionic detergents

Abstract

The micellization of homologous compounds of the types alkyl trimethylammonium alkyl sulphate and alkyl trimethylammonium alkyl sulphonate has been studied. Below the critical micelle concentration these compounds behave like conventional strong 1:1 electrolytes, but the micelles formed above this concentration are substantially uncharged, a circumstance that allows the thermodynamics of the micellization process to be examined. It has been shown that the increments per methylene group for the standard free energy and heat of micellization are similar to those found for non-ionic detergents, and that the large increase in standard entropy that accompanies the micellization process is associated with the change in environment of the hydrophilic head groups.