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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Author: search.filters.author.Ha, Sie-TiongSubject: search.filters.subject.smectic C

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    Synthesis and phase transition behaviours of laterally substituted liquid crystals containing methylhydroquinone: emerging of smectic C phase for higher homologues
    (2017-01-01)
    Seou, Chi-Kien
    ;
    Ha, Sie-Tiong
    ;
    Lee, Siew-Ling
    ;
    Yeap, Guan-Yeow
    ;
    Lin, Chien-Min
    A series of laterally substituted low-molar-mass liquid crystals with molecular geometry were constructed with three phenyl rings bridged through ester central groups as the rigid core and a lateral methyl group as the flexible part of a molecule, with a view to understanding and establishing the effect of molecular structure on liquid crystal behaviour. Low-molar-mass mesogens known as 1,4-bis[(4-n-alkyloxybenzoyl)oxy]toluene with different number of carbon (n) at the alkyl chain have been prepared. Their molecular structures were proposed via physical measurements and spectroscopic techniques. Mesomorphic properties were studied by using differential scanning calorimetry, optical polarizing microscopy and powder X-ray diffraction techniques. The results showed that the melting points as well as the clearing temperatures decreased upon lengthening of the terminal alkyloxy chain lengths. Members with the shorter chain (n = 2-10) exhibited nematic phase. As for higher homologues, members with n = 12, 14, 16 and 18 showed polymorphism, whereby these compounds displayed both smectic and nematic properties.
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    Mesogenic Schiff base esters with benzothiazole core: synthesis and phase transition studies
    (2010)
    Ha, Sie-Tiong
    ;
    Koh, Teck-Ming
    ;
    Yeap, Guan-Yeow
    ;
    Lin, Hong-Cheu
    ;
    Lee, Siew-Ling
    A series of new rod-shaped mesomorphic compounds, 6-ethoxy-2(4-alkanoyloxybenzylidenamino)benzothiazoles, consisting of a 2,6-disubstituted benzothiazole core and a Schiff base central linkage, were synthesized and their structures were ascertained via elemental analysis and spectroscopic techniques. Their mesomorphic properties were studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD) analysis. All compounds showed enantiotropic mesomorphism. Whilst the lower members of the series, hexanoyloxy and octanoyloxy derivatives exhibited nematic phase, the higher members (decanoyloxy, dodecanoyloxy, tetradecanoyloxy, hexadecanoyloxy and octadecanoyloxy derivatives) exhibited nematic and smectic C phases.
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    Synthesis of new schiff base ester liquid crystals with a benzothiazole core
    (2010)
    Ha, Sie-Tiong
    ;
    Koh, Teck-Ming
    ;
    Lee, Siew-Ling
    ;
    Yeap, Guan-Yeow
    ;
    Lin, Hong-Cheu
    A series of new calamitic liquid crystals, 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, comprising a benzothiazole core, terminal methoxy group and a Schiff base linkage were synthesised and characterised. This series comprises 12 members wherein members differ by the length of the alkanoyloxy chain (Cn-1H2n-1COO-, where n = 2-8, 10, 12, 14, 16, 18). Their mesomorphic properties were studied by using differential scanning calorimetry, optical polarising microscopy and powder X-ray diffraction techniques. The short chain derivatives (n = 2 and 3) were non-mesogenic compounds, while an enantiotropic nematic phase was present throughout the remaining members of the series. The smectic C phase emerged from the decanoyloxy derivative onwards.