Change in the aggregational character of the cationic surfactant cetyl trimethyl ammonium bromide in the presence of o- and p-itrophenolates

摘要

The effect of the addition of sodium salts of p-nitrophenol and o-nitrophenol on the structural transition of aqueous micellar solutions of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) was studied by viscosity, 1H nuclear magnetic resonance, and dynamic light scattering measurements. The rapid increase in the relative viscosity of CTAB solutions on the addition of sodium salts of o-nitrophenol and p-nitrophenol was due to the transition in micellar shape from spheres to rods. Dynamic light scattering studies indicated a decrease in the diffusion coefficient of the micelles with the addition of p-nitrophenol. The adsorption and orientation of the salts on the micellar surface and subsequent growth of the micelles was studied by nuclear magnetic resonance.