Dynamic properties of discotic liquid crystals with triphenylene and benzene cores, studied by broadband dielectric spectroscopy
作者:
Herbert Groothues,
Friedrich Kremer,
DavidM. Collard,
C.P. Lillya,
期刊:
Liquid Crystals
(Taylor Available online 1995)
卷期:
Volume 18,
issue 1
页码: 117-121
ISSN:0267-8292
年代: 1995
DOI:10.1080/02678299508036600
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Broadband dielectric spectroscopy in the frequency range from 10−4to 109Hz was employed to study the molecular dynamics of various triphenylene and benzene derivatives in their isotropic and liquid crystalline phases. For all derivatives, two relaxation processes were detected in their columnar mesophases. The β-process shows an Arrhenius-like temperature dependence with activation energies between 37 and 40 kJ mol−1. This process is assigned to a librational motion of the ester groups in the side chains. The β-process follows a Williams-Landel-Ferry temperature dependence and is correlated to the glass transition. This process is assigned to the hindered rotation of the molecular discs around the columnar axis. In the isotropic phase, the dielectric properties of the benzene derivatives are essentially different from the triphenylenes, most probably because of the difference in capability of conformational rearrangement.
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