Browsing by Author "Abe, Kazuma"

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Mesogenic Schiff Base with Bromo End Group: Synthesis and Thermotropic Properties
(2012-08-01)
Ha, Sie-Tiong
;
Lee, Teck-Leong
;
Lin, Hong-Cheu
;
Ito, Masato M.
;
Abe, Kazuma
A new homologous series of Schiff base esters comprising a terminal bromo substituent was studied. The bromo substituent contributes to the molecular polarizability, thus, affecting intermolecular interactions, hence, resulting in smectic polymorphism. The mesomorphic properties were studied using differential scanning calorimeter and polarizing optical microscope attached to a Linkam hotstage. Whilst the lower members, n-ethanoyloxy and n-butanoyloxy derivatives were non-mesogens, n-hexanoyloxy member exhibited monotropic (less stable) smectic A and smectic B phases. Further lengthening of the alkanoyloxy chain from C8 to C12 (medium members), led to formation of enantiotropic (more stable) smectic A and smectic B mesophases based on the observation of both phases during heating and cooling cycles. The high members of the series, C14, C16 and C18 exhibited enantiotropic smectic A phase and monotropic smectic B phase. The homologous members were compared with structurally related series to establish their chemical structure-mesomorphic behaviour relationships.
Mesomorphic behavior of new benzothiazole liquid crystals having Schiff base linker and terminal methyl group
(2012-07-01)
Ha, Sie Tiong
;
Foo, Kok Leei
;
Lin, Hong Cheu
;
Ito, Masato M.
;
Abe, Kazuma
"A homologous series of heterocycles, 6-methyl-2-(4-alkoxybenzylidenamino)benzothiazoles, were synthesized and characterized using FT-IR, H-1 and C-13 NMR and mass spectrometric analysis. Enantiotropic nematic phase was observed for shorter members. Smectic A phase only emerged from octyloxy derivative onwards. The terminal methyl group at the benzothiazole fragment and the Schiff base linkage influenced the mesomorphic behavior of the present series. (C) 2012 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved."