Effect of Temperature on Micelle Formation in Aqueous NaBr Solutions of Octyltrimethylammonium Bromide.

Association processes in aqueous solutions of octyltrimethylammonium bromide, C(8)TAB, have been studied in aqueous NaBr solutions at temperatures from 20 to 55 degrees C. The values of the critical micelle concentration, CMC, were determined from the intersections of two straight line portions of the plots of the relationship between adiabatic compressibility of the solutions and surfactant concentration. The value of the CMC thus determined exhibits minima at a certain temperature, T(min). The value of T(min) shifts toward a lower temperature with increasing NaBr concentration. Based on the most probable micelle size model, the values of thermodynamic functions of micelle formation have been estimated at various temperatures. Copyright 2001 Academic Press.