Berlin 2018 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 68: Poster: Complex Fluids, Glasses, Granular
DY 68.17: Poster
Donnerstag, 15. März 2018, 15:30–18:00, Poster A
2H and 17O NMR studies of dynamics of water-ethylene glycol mixtures — •Verena Fella, Dominik Demuth, and Michael Vogel — TU Darmstadt, Condensed Matter Physics, Darmstadt, Germany
Binary water mixtures play an important role in biological as well as technological systems. Particularly water-alcohol mixtures are used in many applications though a complete understanding of their complex dynamical behaviour is still lacking. Here, nuclear magnetic resonance (NMR) experiments prove to be a powerful tool due to isotope selective measurements. 2H NMR is an established method to analyse mixtures by deuterating one component. Unfortunately, selective observation of water in water-alcohol mixtures is hampered by deuteron exchange. Adjei-Acheamfour et al. (J. Chem. Phys., 143, 214201 (2015)) recently investigated ultraslow dynamics in ice with 17O NMR by selective excitation of the central line. This approach yields many new possibilities to explore glass-forming materials. We combine 17O and 2H NMR to analyse a mixture of H217O and deuterated ethylene glycol (EG-d4) where each component can be measured separately. Correlation times τ in the range from 10−10 to 10−5 s show a strong coupling between the water and EG dynamics. For the supercooled phase the correlation times exhibit a broad distribution, so that 17O NMR studies at τ>10−5 s are limited by short spin-lattice relaxation times T1. However, we show that 17O NMR yields valuable insights into the crystalline phase of water-EG mixtures. In the future this can be exploited to study crystallisation in various aqueous systems.