Odd-even effects in the thermotropic and optical properties of three series of chiral twin liquid crystals
作者:
AntoniusT. M. Marcelis,
Arie Koudijs,
ErnstJ. R. Sudhölter,
期刊:
Liquid Crystals
(Taylor Available online 1995)
卷期:
Volume 18,
issue 6
页码: 843-850
ISSN:0267-8292
年代: 1995
DOI:10.1080/02678299508036701
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Three series of novel chiral twin liquid crystals consisting of a cholesteryl and a 4′-cyanobiphenyl-4-yloxy group (III) or a 4-cyanophenoxy group (IV) and of a dihydro-cholesteryl and a 4′-cyanobiphenyl-4-yloxy group (V) connected by an alkanoate spacer with a varying number (1–7 and 10) of methylene units were synthesized and their mesogenic properties investigated. Strong odd-even effects were observed as a function of spacer length for the phase transition temperatures, the corresponding entropy changes and the selective reflection wavelengths associated with the chiral nematic phase. The compounds with an even number of methylene units have a smaller pitch than the compounds with an odd number of methylene units. Replacement of the cholesteryl group by a dihydrocholesteryl group results in an larger pitch, whereas replacement of the 4′-cyanobiphenyl-4-yloxy group by a 4-cyanophenoxy group gives a smaller pitch.
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