Conductivity Dynamics and Static Dielectric Permittivity of Highly Conducting Molecular Liquids Studied with Impedance Spectroscopy. Formamides

Abstract

Impedance spectroscopy was used for studies of the frequency dependence of the electric conductivity of two highly conducting liquid amides: N-methylformamide (NMF), strongly self-associated via the hydrogen bonds C=O...N-H, and N,N-dimethylformamide (DMF), which is not able to self-organize by hydrogen bonding. The studies were performed in the frequency range f = 50 kHz-100 MHz and in the temperature range T = 278.15-363.15 K. It was found that, at a given temperature, NMF exhibits static conductivity (sigma(0)) of 2 orders of magnitude higher, and conductivity relaxation time (tau(sigma)) of 2 orders of magnitude shorter, than those of DMF. On the basis on sigma(0) and tau(sigma) values, the static dielectric permittivity (epsilon) was calculated for both liquids studied and the values obtained perfectly agree with those measured with the classical dielectric methods. An empirical equation for epsilon(T) dependence for NMF and DMF is proposed.