Browsing by Author "Subramaniam, Ramesh T."

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Synthesis and mesomorphic evaluation of new calamitic liquid crystals containing benzothiazole core
(2011-05-01)
Koh, Teck Ming
;
Ha, Sie Tiong
;
Lee, Teck Leong
;
Lee, Siew Ling
;
Yeap, Guan Yeow
The design and synthesis of new calamitic benzothiazole-based liquid crystals, 2[4-(4-alkyloxybenzoyloxy)-phenyl]benzothiazoles are presented. The target compound was characterized using spectroscopic techniques, such as FT-IR, NMR ((1)H and (13)C), microanalysis and EI-MS. The liquid crystalline behaviours of these compounds were thoroughly examined by differential scanning calorimetry and polarizing optical microscope techniques. These materials exhibited enantiotropic nematic phase with high thermal stability (> 168 degrees C). Smectic A phase starts to emerge as monotropic (metastable) phase from C10 member and changes into enantiotropic (stable) phase from C12 and persists up to C16 members. (C) 2010 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Synthesis and Mesomorphic Properties of 4-(Methylthio)benzylidene-4 '-n-alkanoyloxyanilines
(2011-10-01)
Ha, Sie-Tiong
;
Lee, Teck-Leong
;
Yeap, Guan-Yeow
;
Lin, Hong-Cheu
;
Ito, Masato M.
A homologous series of Schiff base esters, 4-(methylthio)benzylidene-4'-n-alkanoyloxyanilines possessing even number of carbon atoms at the alkanoyloxy chain (C(n-1)H(2n-1)COO, n = 2 to 18) was synthesized. The structure of the 4-(methylthio)benzylidene-4'-n-alkanoyloxyanilines was confirmed by elemental analysis and spectroscopic techniques including FT-IR, (1)H and (13)C NMR and EI-MS. Mesomorphic properties were evaluated by differential scanning calorimetry and polarizing optical microscopy techniques. Whilst n-butanoyloxy to n-octanoyloxy derivatives exhibited monotropic nematic phase, n-ethanoyloxy and n-decanoyloxy to n-octadecanoyloxy derivatives were non-mesogenic compounds. The mesomorphic properties of the present series were compared with other structurally related series to establish the chemical structure-mesomorphic property relationship.