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Invited Article

Synthesis, mesomorphic behaviour and optical anisotropy of some novel liquid crystals with lateral and terminal fluoro substituents and a 2,6-disubstituted naphthalene core

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Pages 877-886 | Received 08 Sep 2014, Published online: 27 Mar 2015
 

Abstract

The synthesis, mesomorphic properties and optical anisotropy of a range of diphenylnaphthalenes are detailed. One phenyl ring contains two lateral ortho fluoro substituents, with either a terminal butoxy chain or a pentyl chain; in both cases, the other phenyl ring possesses one, two or three fluoro substituents at the end of the molecule. The synthesis of the materials was effected efficiently using a combination of low-temperature lithiations and Suzuki palladium-catalysed cross-coupling reactions. All six novel compounds exhibit the nematic phase at very high temperature (between 125°C and 245°C), particularly those with fewer lateral fluoro substituents, and all show a smectic A phase. The melting points are rather high, but those compounds with a terminal pentyl chain and more lateral fluoro substituents do have much lower melting points (around 100°C). As expected from naphthalene liquid crystals, the optical anisotropy (measured as extrapolated values at 25°C) is very high (0.27–0.35), particularly for those compounds with a terminal butoxy chain and fewer lateral fluoro substituents.

Acknowledgements

We thank the Department of Chemistry, University of Hull, for providing research facilities and Kingston Chemicals Limited for the providing several chemicals.

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