DIELECTRIC-SPECTROSCOPY ANALYSIS ON THE INTERFACIAL COMPOSITION OF NONIONIC MICELLAR SOLUTIONS

By iterative use of a suitable mixture equation for the dielectric per mittivity of heterogeneous systems we investigate C(12)E(6) solutions as a function of the monomer concentrations and of the temperature at four different solvent compositions: 0, 2, 4 and 6 molar urea in water . With this methodology we obtain the permittivity of the micellar hea d group crown termination as a function of the hydrated volume of the monomer head group, composed in our case by 6 PEO (polyethylene oxide) units and by the interdigitated solvent molecules. Then the intercept between the dielectric behaviour as a function of the PEO molar conce ntration of the micellar crown region and of a solution of PEG-water-u rea gives an estimate of the actual composition within the interface, at a fixed temperature and solvent composition. Our results suggest a temperature dependence of the degree of hydration at the micellar inte rface in pure water solution. With mixed water-urea solutions, cosolve nt adsorbtion at the micellar interface is observed.