Kampar, Malaysia
Kampar, Malaysia

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Ha S.-T.,Jln University | Lee T.-L.,Jln University | Lin H.-C.,National Chiao Tung University | Ito M.M.,Soka University | And 3 more authors.
Asian Journal of Chemistry | Year: 2012

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.

Ha S.T.,Jln University | Foo K.L.,Jln University | Subramaniam R.T.,University of Malaya | Ito M.M.,Soka University | And 2 more authors.
Chinese Chemical Letters | Year: 2011

New Schiff base liquid crystals containing benzoxazole core and alkanoyloxy chain at the end group of the molecules (C n-1H 2n-1COO-, n = 14, 16, 18) was synthesized. The present compounds are enantiotropic smectic A liquid crystals. It was also found that the end groups of the molecules and polar chloro substituent at the benzoxazole fragment had effect on the mesomorphic properties. © 2011 Sie Tiong Ha.

Ha S.-T.,Jln University | Yeap G.-Y.,Universiti Sains Malaysia | Boey P.-L.,Universiti Sains Malaysia
E-Journal of Chemistry | Year: 2012

A series of elongated Schiff base esters containing three aromatic rings with hexadecanoyl chain as one of the terminal group and various R substituents (R = CN, OH, SH, and NO2) at the other end of molecule were prepared, and their structures were confirmed via physical measurement. The thermotropic properties of these compounds were investigated via differential scanning calorimetry and polarizing optical microscopy. The thermal data indicate that all of these compounds exhibit mesomorphic properties. Whilst compounds with R = OH, SH and NO2 show nematic phases, compound containing cyano substituent are smectogenic in nature. © 2012 Hindawi Publishing Corporation.

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