Liquid crystalline compounds in the thiophene series. VIII. Synthesis and characterization of liquid crystalline vinylenes with thiophene moieties and carbaldehyde groups
作者:
G. Koßmehl,
F.D. Hoppe,
期刊:
Liquid Crystals
(Taylor Available online 1993)
卷期:
Volume 15,
issue 3
页码: 383-393
ISSN:0267-8292
年代: 1993
DOI:10.1080/02678299308029139
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
New thermotropic liquid crystal compounds, with one and two mesogenic groups, have been synthesized and characterized. The structural elements of the compounds consist of thiophene ring systems, vinylene units and, for some compounds, carbaldehyde groups. Mesogenic groups involving three thiophene ring systems are normally not liquid crystalline. Only in the case ofE,E-5-[5-(5-butyl-2-thienylvinyl)-2-thienylvinyl]-2-thiophenecarbaldehyde could a monotropic nematic phase be easily observed. By replacing thiophene ring systems in the core with a benzene ring system, or by attaching one carbaldehyde group at the moieties, or by doubling the mesogenic groups via an alkylene spacer, the temperature ranges of the mesophases of the compounds with thiophene ring systems can be enlarged or liquid crystal phases induced. The small values for δSNI, which have been observed for the low molecular weight compounds, indicate a very low order in the nematic phases.
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