This title appears in the Scientific Report : 2020 
Complex molecular dynamics of a symmetric model discotic liquid crystal revealed by broadband dielectric, thermal and neutron spectroscopy
Yildirim, Arda
Krause, Christina / Zorn, Reiner / Lohstroh, Wiebke / Schneider, Gerald Johannes / Zamponi, Michaela / Holderer, Olaf / Frick, Bernhard / Schönhals, Andreas (Corresponding author)
Neutronenstreuung; JCNS-1
Heinz Maier-Leibnitz Zentrum; MLZ
Neutronenstreuung; ICS-1
JCNS-FRM-II; JCNS-FRM-II
Soft matter, 16 (2020) 8, S. 2005-2016
London Royal Soc. of Chemistry 2020
10.1039/C9SM02487E
32003764
Journal Article
FRM II / MLZ
Soft Matter, Health and Life Sciences
Jülich Centre for Neutron Research (JCNS)
Functional Macromolecules and Complexes
Soft Condensed Matter > 0
Basic research > 0
Restricted
Restricted
Published on 2020-01-24. Available in OpenAccess from 2021-01-24.
Please use the identifier: http://dx.doi.org/10.1039/C9SM02487E in citations.
Please use the identifier: http://hdl.handle.net/2128/24659 in citations.


The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized γ-relaxation at lower temperatures and a so called α2-relaxation at higher temperatures. The relaxation rates of the α2-relaxation have a complex temperature dependence and bear similarities to a dynamic glass transition. The relaxation rates estimated by Hyper DSC, Fast Scanning calorimetry and AC Chip calorimetry have a different temperature dependence than the dielectric α2-relaxation and follow the VFT-behavior characteristic for glassy dynamics. Therefore, this process is called α1-relaxation. Its relaxation rates show a similarity with that of polyethylene. For this reason, the α1-relaxation is assigned to the dynamic glass transition of the alkyl chains in the intercolumnar space. Moreover, this process is not observed by dielectric spectroscopy, which supports its assignment. The α2-relaxation is assigned to small scale translatorial and/or small angle fluctuations of the cores. The neutron scattering data reveal two relaxation processes. The process observed at shorter relaxation times is assigned to the methyl group rotation. The second relaxation process at longer time scales agree in the temperature dependence of its relaxation rates with that of the dielectric γ-relaxation.