Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Liquids and Ionic Liquids

CPP 44.1: Topical Talk

Thursday, March 25, 2010, 09:30–10:00, H45

Glassy dynamics and charge transport in ionic liquids — •Friedrich Kremer, Joshua Sangoro, Ciprian Iacob, and Jörg Kärger — Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, 04103, Leipzig, Germany

Charge transport and glassy dynamics in a variety of glass-forming ionic liquids (ILs) are investigated in a wide frequency and temperature range by means of Broadband Dielectric Spectroscopy(BDS), Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR), ac Calorimetry, Differential Scanning Calorimetry and Rheology. The dielectric spectra are dominated - on the low-frequency side - by electrode polarization effects while, for higher frequencies, charge transport in a disordered matrix is the underlying physical mechanism. While the absolute values of dc conductivity and viscosity vary over more than 11 decades with temperature and upon systematic structural variation of the ILs, quantitative agreement is found between the characteristic frequency of charge transport and the structural α-relaxation. This is discussed within the framework of the concept of dynamic glass transition driven hopping traced back to Einstein, Einstein-Smoluchowski, and Maxwell relations. A novel approach is applied to extract diffusion coefficients from BDS spectra in quantitative agreement with PFG NMR values but in a much broader range. It becomes possible to extract from the dielectric spectra separately the number density and the mobilities of the charge carriers and the type of their thermal activation.