EFFECT OF TEMPERATURE ON THE MIXED MICELLAR TETRADECYLTRIMETHYLAMMONIUM BROMIDE BUTANOL SYSTEM

The TTAB-butanol system has been studied over a temperature range of 1 5 to 35 degrees C and at butanol concentrations up to 0.3 mol/kg. The CMC vs temperature curves have a smooth minimum whose location is not markedly influenced by alcohol presence. The molar fraction of butanol in the micelles and the entropy of micellization have been calculated using a theoretical treatment of critical micelle concentration data based on excess thermodynamic quantities. The heat capacity of micelli zation has been obtained and compared with results predicted by a rece nt thermodynamical theory which describes a universal behavior exhibit ed by ionic surfactants. Both the entropy and the enthalpy of micelliz ation increase with alcohol concentration. The butanol molar fraction in micelles enables us to estimate the standard free energy of solubil ization, which is found to decrease with temperature. It is important to emphasize the chance of predicting the value of these interesting t hermodynamic quantities without the need for measuring them. The degre e of micelle ionization has also been evaluated using two different me thods, and no significant differences have been observed. (C) 1997 Aca demic Press.