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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 21: Glasses and Glass Transition 2 (joint session DY/CPP)
CPP 21.5: Vortrag
Mittwoch, 24. März 2021, 12:20–12:40, DYc
Glassy dynamics in viscous liquids - Prospects of broadband NMR relaxometry — •Manuel Becher1,2, Michael Vogel2, and Ernst Rössler1 — 1Nordbayerisches NMR-Zentrum, Universität Bayreuth, Germany — 2Institute of Condensed Matter Physics, TU Darmstadt, Germany
As the molecular dynamics of a liquid undergoing a glass transition features a wide range of timescales over many decades, it is beneficial to study these viscous liquids with broadband spectroscopic techniques. Besides well established methods such as dielectric spectroscopy (DS) and depolarized dynamic light scattering (DDLS) covering many decades in time/frequency, also nuclear magnetic resonance (NMR) offers detailed insights in molecular motion ranging from the boiling point of a liquid to its glassy arrest. However, in most recent publications the spectral shape of the main relaxation peak between DS, DDLS and NMR was readressed and the question of universality arised, rendering the prospect of broadband NMR experiments to a new importance. As NMR experiments can provide single-particle correlation functions of the probed molecular moieties, but are usually carried out at a single Larmor-frequency, interest lies in ’broadening’ their frequency range. In this talk, ways to access the relaxation spectrum are presented, focussing on field-cycling (FC) NMR. Here, recent advances allow us to evaluate the concept of frequency-time superposition in molecular glass formers. Moreover, making use of NMR’s isotope sensitivity, molecular site-dependent measurements are shown to reveal the impact of molecular flexibility on structural relaxation.