Effects of Sodium Bromide Salt and Temperature on the behaviour of Aqueous Solution of Cetyltrimethylammonium Bromide

Abstract

The effects of sodium bromide(NaBr) salt and temperature on the aggregation behaviour of cetyltrimethylammonium bromide (CTAB) have been studied using conductivity data.Conductivity was observed to vary increasingly with both temperature and salt concentration. The critical micelle concentration (CMC) of CTAB decreased with increase in the concentration of NaBr but increased as temperature increased. For example,the CMCs of CTAB in 0.0 and 10.0mM solutionsof NaBr at 30 C were 1.68 and 1.50 mMrespectively while those of the same concentrations at 35 C were 1.84 and 1.63respectively.It wasalso found that both salt and temperature influenced the degree of micelle ionization as well as the free energy of micellization. Results also showedthat the stability of CTAB micelles was enhanced by adding NaBr molecules.These observations have been discussedin terms of the electrostatic repulsion of charged CTAB head group.