Effect of Urea on the Thermodynamics of Hexadecyltrimethylammonium Bromide Micelle Formation in Aqueous Solutions

Resumo

The effect of urea on the thermodynamics of hexadecyltrimethylammonium bromide (CTAB) micelle formation in aqueous urea solutions was studied by isothermal titration microcalorimetry. The thermodynamic functions of ΔH, ΔG, and ΔS of CTAB micelle formation were calculated. The critical micelle concentrations (CMC) were determined. The addition of urea to the solution decreased the micelle formation entropy. This was attributed to the “lowering” of the structural temperature of the solution, which led to an increased number of hydrogen bonds and structure formation of water.