Charge transport and glassy dynamics in imidazole-based liquids

Abstract

Broadband dielectric spectroscopy, differential scanning calorimetry, rheology, and pulsed field gradient–nuclear magnetic resonance (PFG NMR) are combined to study glassy dynamics and charge transport in a homologous series of imidazole-based liquids with systematic variation of the alkyl chain length. The dielectric spectra are interpreted in terms of dipolar relaxation and a conductivity contribution. By applying the Einstein, Einstein–Smoluchowski, and Stokes–Einstein relations, translational diffusion coefficients—in quantitative agreement with PFG NMRmeasurements—are obtained. With increasing alkyl chain length, it is observed that the viscosity increases, whereas the structural α -relaxation rate decreases, in accordance with Maxwell’s relation. Between the rate ω e of electrical relaxation and the rate ω α of the structural α -relaxation, scaling is observed over more than six decades with a decoupling index of about 2.