Effect of ethanol on the aggregation properties of cetyltrimethylammonium bromide surfactant

Surfactant aggregation properties in aqueous and mixed organic/aqueous solutions have attracted considerable interests especially for the applications to the template synthesis of nanoporous inorganic materials. In this work, we study the aggregation behavior of cetyl trimethylammonium bromide surfactant in both aqueous and mixed water/ethanol solutions by the steady-state fluorescence probe technique. The critical micelle concentration (CMC) and the micelle aggregation number were determined in solutions with different ethanol contents. The CMC increases and the aggregation number decreases with increasing ethanol content in solutions. The effect of ethanol on the micelle formation can be treated as a structure breaking process. The density functional theory was used to calculate the charge density distribution over the surfactant molecules in different solvents. The results obtained reveal that the micelle size distribution in solutions can be adjusted by varying the content of ethanol in solvents.