Polar nematictrans-4-substituted-cyclohexyl (E)-alk-2-enoates The influence of dipoles and double bonds on the transition temperatures and other physical properties
| Autor: | Hubert Seiberle, Stephen M. Kelly, Martin Schadt |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Liquid Crystals. 18:581-594 |
| ISSN: | 1366-5855 0267-8292 |
| DOI: | 10.1080/02678299508036661 |
| Popis: | As part of a systematic study of the factors affecting nematic phase formation, the influence of introducing dipoles (in the form of oxygen, carbonyl and carboxy groups) and steric restrictions (in the form of carbon-carbon double bonds) in various positions, configurations and combinations in a model system (4-[trans-4-pentylcyclohexyl]benzonitrile) has been investigated. On the basis of these results, we have introduced an ester group and a carbon-carbon double bond with a trans-configuration (E) into the terminal alkyl chain attached to the cyclohexyl ring of a variety of two- and three-ring nematic mesogens of positive dielectric anisotropy. This is a new combination of a polar ester group (dipole effect) and the added rigidity imposed by the double bond (steric effect). Most of the new (E) alk 2-enoates containing two rings in the molecular core possess high melting points. Only a few two ring esters exhibit nematic phase, although the clearing point of those esters exhibiting mesomorphic be... |
| Databáze: | OpenAIRE |
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