Dresden 2020 – wissenschaftliches Programm
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CPP 60.4: Vortrag
Mittwoch, 18. März 2020, 12:30–12:45, ZEU 222
Local dynamics of ionic liquids studied by 2H NMR — •Elisa Steinrücken, Manuel Becher, and Michael Vogel — TU Darmstadt, Institut für Physik kondensierter Materie, Hochschulstr. 6, 64289, Darmstadt, Germany
Room Temperature Ionic Liquids (RTIL) are molten salts at ambient temperatures with a low vapour pressure. They are usually glass forming systems with complex and heterogeneous molecular dynamics. The combination of different cations and anions opens wide ranges of chemical and physical applications. Hence, a fundamental understanding of molecular dynamics is of crucial importance. Here, RTILs consisting of imidazole-based cations and [Tf2N]− or [BF4]− anions are in the experimental focus. Nuclear Magnetic Resonance (NMR) provides access to dynamics in wide ranges of time and length scales [M. Becher, E. Steinrücken, M. Vogel, J. Chem. Phys., 2019]. Due to its isotope selectivity the dynamical behaviour of the two components can be distinguished. Performing 2H NMR experiments on selectively deuterated cations, we gain deep insights into their microscopic rotational dynamics. When combining 2H spin-lattice relaxation (SLR) and stimulated-echo (STE) experiments, rotational correlation times of the cation are accessible from the fast motion in the liquid to slow glassy dynamics. Furthermore, we exploit that STE experiments and 2H line-shape analysis provide information about the mechanism for rotational motion. Altogether, we show that application of 2H NMR to RTIL has a high potential for the characterization of time scales and motional mechanisms of the molecular dynamics.