Conductivity enhancement, dielectric relaxation, and non Arrhenius trends in octanoic acid / bis(2-ethylhexyl) amine binary mixtures

Binary mixtures of the amphiphilic materials octanoic acid and bis(2-ethylhexyl) amine, have been investigated by broadband dielectric spectroscopy as a function of temperature. Depending on the composition, the dc conductivity of the mixture is several orders of magnitude higher than that of the pure components at room temperature. The higher the conductivity of the mixture, the lower is the relaxation frequency at which the dielectric relaxation occurs. Moreover, non Arrhenius trends of the dc conductivity and of the dielectric relaxation time vs. temperature have been observed for some of the mixtures above their melting temperature. The formation of transient eteroadducts of OA and BEEA molecules, most likely 2(OA):BEEA, could be responsible for the conductivity enhancement versus composition, as well as for the increase of the viscosity, and for the slowing down of the dielectric relaxation. This picture, supported by the results of Wide Angle X rays Scattering and 1H-NMR measurements, can also account for the peculiar temperature dependence of the dc conductivity and of the dielectric relaxation.