INTERFACIAL CONFORMATION AND COMPOSITION OF C(12)E(6) MICELLE IN WATER INFERRED BY DIELECTRIC-SPECTROSCOPY

An iterative use of a suitable mixture equation for dielectric permittivity of heterogeneous systems can give direct information on the permittivity of the micellar head group crown, composed in the present case of six PEO terminations and of interdigitated water molecules. The results are obtained giving as a free parameter the actual conformation of the head group chains, i.e., the thickness of the micellar crown, l(h), that defines the available volume for water molecules too. The dielectric behaviour of the crown region is compared with that obtained from PEG-water mixtures to estimate the actual value of l(h) at each temperature. The number of interdigitated water molecules per PEO unit, n(w), can then be extracted. The temperature dependence of l(h) and n(w) shows a saturation near the critical temperature.