Dresden 2017 – wissenschaftliches Programm
CPP 42.6: Vortrag
Mittwoch, 22. März 2017, 16:45–17:00, ZEU 114
Dynamics of Room Temperature Ionic Liquids: A 1H and 19F NMR Relaxometry and Diffusiometry study — •Manuel Becher and Michael Vogel — TU Darmstadt Solid State Physics, Darmstadt, Germany
Room Temperature Ionic Liquids (RTIL) are salts with a low melting point and vapour pressure, caused by a rather big and asymmetric cation. They are usually glass forming systems with complex and heterogeneus molecular dynamics. The combination of different cations and anions opens wide ranges of chemical and physical applications, e.g. as solvents or fluid electrolytes, and their optimization. Hence, a fundamental understanding of molecular dynamics is of crucial importance. Here, imidazolium based RTILs with an [Tf2N]− anion are in the experimental focus, with a variation of alkyl chain lengths at the cation so as to vary structural and dynamical heterogeneity. Nuclear Magnetic Resonance (NMR) provides access to glassy dynamics in wide range of temperature and length scales. Due to its isotope sensitivity the dynamical behaviour of different molecules/molecular groups can be separated. In a static field gradient, we measure the self-diffusion coefficient of the cation (1H) and anion (19F), revealing hints to clustering. Field-Cycling relaxometry provides frequency-dependent relaxation times T1(ω) and yields translational and rotational correlation times as well as insight into local dynamics. Comparing long-range self-diffusion with short-range structural relaxation, we analyze cation-anion couplings against the background of alkyl-chain length dependent structural heterogeneities.