Non-symmetric chiral isoflavone dimers: synthesis,characterisation and mesomorphic behaviour |
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Authors: | Guan-Yeow Yeap Tze-Nee Chan Wan-Sinn Yam Damian Pociecha Ewa Gorecka |
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Institution: | 1. Liquid Crystal Research Laboratory, School of Chemical Sciences , Universiti Sains Malaysia , Penang , Malaysia;2. Department of Chemistry , University of Warsaw , Warsaw , Poland |
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Abstract: | A new series of non-symmetric chiral isoflavone-based liquid crystalline dimers, α-(2-methylbutyl-4′-(4″-phenyloxy)benzoate)-ω-(3-(4′-decyloxyphenyl)-4H-1-benzopyran-4-one-7-oxy)alkanes, with 3–12 carbon atoms in the alkyloxy spacer, have been synthesised. A pronounced odd–even effect for the phase transition temperatures upon varying the spacer length was observed. The short dimers exhibited monolayer smectic A (SmA) and smectic C (SmC*) phases while for longer homologues a chiral nematic (N*) phase was found. The temperature range of the nematic phase was broadened with elongation of the alkyl spacer. Stabilisation of the nematic phase resulted from competition between the monolayer and intercalated smectic structures. The SmA–SmC* phase transition was second order for all studied compounds with a cross over to the de Vries type behaviour for the shortest homologue. |
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Keywords: | liquid crystals chirality non-symmetric chiral dimers isoflavonoids phase transition |
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