Polarity and steric effect of the lateral substituent on the mesophase behaviour of some newly prepared liquid crystals |
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| Authors: | Magdi M. Naoum Nadia H. Metwally Manal M. Abd eltawab Hoda A. Ahmed |
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| Affiliation: | 1. Department of Chemistry, Faculty of Science, Cairo University, Cairo, Egyptmagdinaoum@yahoo.co.uk;3. Department of Chemistry, Faculty of Science, Cairo University, Cairo, Egypt |
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| Abstract: | Eight homologous series of 2- (or 3-) substituted phenyl 4?-(4?-alkoxy phenylazo) benzoates (Ina–h) were prepared in which, within each homologous series, the length of the terminal alkoxy group varies between 6, 8, 10 and 12 carbons, while the other substituent, X, is a laterally attached polar group that alternatively changed from CH3, H, F, Br and CN. Compounds prepared were characterised by infrared and 1H-NMR spectroscopy, and their mesophase behaviour investigated by differential scanning calorimetry and identified by polarised light microscopy. The results were discussed in terms of polarity and steric effects. The stability of the mesophase was correlated once with the dipolar anisotropy of the whole molecule and another with the dipolar anisotropy of the substituent, X. A comparative study was made between the investigated compounds and their previously prepared linear 4-substituted isomers, namely 4-substituted phenyl 4?-(4?-alkoxy phenylazo) benzoates (Ini–k). |
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| Keywords: | 2- (or 3-) substituted phenyl 4?-(4?-alkoxy phenylazo) benzoates mesophase behaviour dipole moment dipolar anisotropy |
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