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    题名: 含不對稱多雜環分子之液晶相行為探討
    作者: 胡倩瑜;Hu,Chien-Yu
    贡献者: 化學學系
    关键词: 液晶;雜環;liquid crystal;pyrazole;oxadiazole;isoxazole
    日期: 2016-07-13
    上传时间: 2016-10-13 12:40:34 (UTC+8)
    出版者: 國立中央大學
    摘要: 系列一主要是探討含多雜環分子液晶表現,微觀去觀察雜環如何影響液晶行為,成功合成出含有isoxazole、oxadiazole、pyrazole兩兩組合成的不對稱雜環且位相不同之1a、1b;2a、2b; 3a、3b化合物,證實相異雜環對於液晶有極大影響,且分子中間三雜環越趨向線性之結構,其液晶行為表現較佳。透過2b單晶結構,研究雜環可以誘導出何種作用力並模擬出液晶相時排列,利用成功養出的3a單晶結構,得知雜環之間作用力,也進而得知分子形狀會影響液晶表現。
    系列二合成設計出含OH基團之雜環結構,觀察有無OH基團及雜環的不同對液晶相所造成之影響;可以觀察到含有pyrazole的I4a澄清點比含有isoxazole的4a來的高且液晶行為較佳,透過I4a的單晶資訊得知I4a分子間以強氫鍵連接,因此澄清點較高液晶範圍較廣。OH基團能提供氫鍵使分子排列規則,因此含有OH基團的4a比I4b的澄清點要來的高,且出現黏滯性大、流動性差的SmX液晶相;搭配變溫IR可鑑定特定基團,藉由升降溫觀察peak的變化,發現從固態到液態的過程中,分子的作用力的確有所變化。
    ;In the first series, for new series of unsymmetric isoxazoles、pyrazoles and 1,3,4-oxadiazoles were prepared, characterized and their mesomorphic properties investigated. Isoxazoles were obtained by condensationcyclization of –diketones with hydroxylamine hydrochloride in refluxing THF,and pyrazoles obtained by condensationcyclization of –diketones with hydrazine in refluxing THF,while 1,3,4-oxadiazoles were obtained from hydrazine–carboxylate in refluxing POCl3.The data indicated that all compounds with meta-substituted benzene1b、3bwere not mesogenic. Interestingly, the other series of compounds with para-substituted benzene1a、2a、3aexhibited N/ SmC /SmA phases. The formation of mesophases in 1a、2a、3a might be attributed to the better linear molecular shapes. In contrast, all compounds 1b、3b were more likely bent-shaped,for mesomorphic.
    In the second series, a system of isoxazole containing function group of hydroxyl, performed reaction of condensation reaction then exhibition mesomorphic properties was synthesize and examined. 4a exhibited SmX/SmC phase. Results indicated that increasing the pryazoles would raise the isotropic temperatures and increasing the OH function group would supply hydrogen bonds for molecular arrangement regularity. These mesomorphic properties were studied and identified by polarization microscopy, differential scanning calorimetry, and X-ray diffraction methods.
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