Stopped-flow and solubility studies were used to ascertain the effect 0−7 M urea had upon the micellization of anionic surfactants with sodium decyl sulfate (SDeS) as the surfactant of choice. The complexation of Ni2+ ion with the ligand trans-pyridine-2-azo-p-dimethylaniline (PADA) was the probe reaction for the stopped-flow investigation. The addition of urea increased the critical micelle concentration, and attenuated the rate enhancement ordinarily seen with this complexation in SDeS micellar solution. Urea interacted positively with water in the sense that the complexation rate doubled at 7 M urea with no surfactant present. In micellar solution, urea rendered the SDeS micelles far less accommodating to both Ni2+ ion and PADA which indicated that both the surface and core micellar regions were considerably urea modified especially beyond 4 M urea.

No abstract