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Browsing by Author "WEN, JS"

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    LIQUID-CRYSTALLINE POLYMERS CONTAINING MACROCYCLIC POLYETHERS .2. SIDE-CHAIN LIQUID-CRYSTALLINE COPOLYSILOXANES CONTAINING MESOGENIC UNITS BASED ON 1,3-DIOXANE-2,5-DIYL AND BENZO[15]-CROWN-5
    (1991-10-01)
    HSIUE, GH
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    WEN, JS
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    HSU, CS
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    應用化學系
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    Department of Applied Chemistry
    Synthesis and characterization of a series of copolysiloxanes containing crown ether and trans-1,3-dioxane based mesogens are presented. The phase behaviour of the copolymers was studied using differential scanning calorimetry and optical polarizing microscopy and compared with the phase behaviour of the corresponding copolysiloxane-containing crown ether and biphenyl-based mesogens. Two copolysiloxanes containing trans-2-(benzo-[15]crown-5)-5-(omega-alkan-1-yloxy)-1,3-dioxane side groups present no liquid-crystalline behaviour. The other four copolysiloxanes exhibit a nematic mesophase and undergo side-chain crystallization at low temperature. Two of the four copolysiloxanes which contain a trans-1,3-dioxane-2,5-diyl group in the mesogenic unit present lower isotropization temperatures and narrower mesophase ranges than the other two. This result reveals that replacing a phenyl ring in the mesogenic unit of a liquid-crystalline polymer by a trans-1,3-dioxane ring will decrease the thermal stability of the mesophase exhibited by this polymer.
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    SYNTHESIS AND CHARACTERIZATION OF LIQUID-CRYSTALLINE COPOLYSILOXANES CONTAINING AZOBENZENE DYES AND 1,3-DIOXANE BASED MESOGENIC SIDE GROUPS
    (1993-02-01)
    HSIUE, GH
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    WEN, JS
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    HSU, CS
    ;
    應用化學系
    ;
    Department of Applied Chemistry
    The synthesis and characterization of nine side-chain liquid crystalline copolysiloxanes containing trans-5-(n-undecanyl)-2-(4-cyanophenyl)-1,3-dioxane and 4-(alkanyloxyphenylazo)benzonitrile side groups are presented. The azobenzene dye contents in the copolymers range from about 5 to 20 wt.-%. The nature of the mesophase exhibited by the copolysiloxanes depends very much on the dye concentration. Three copolysiloxanes which contain about 5 wt.-% azobenzene dye, display a smectic A phase while the other six copolysiloxanes which contain more then 10 wt.-% azobenzene dye, exhibit a nematic phase. All the obtained copolysiloxanes show a very low glass transition temperature and a very wide temperature range of mesophase.