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    Title: 微調分子間作用力調控液晶性質 : 六炔苯基苯盤形分子及1,2,4,5-四炔聯苯基苯板形分子之合成與液晶性質探討
    Other Titles: Manipulations of liquid crystal behaviors by modulations of intermolecular interactions : synthesis and mesogenic properties of disclike hexaynylbenzenes and board-like 1,2,4,5-tetraynylbenzenes
    Authors: 陳秀慧;Chen, Hsiu-hui
    Contributors: 淡江大學化學學系碩士班
    施增廉;Shih, Tzenge-lien
    Keywords: 雙軸性向列型液晶;接觸置備法;室溫盤形向列液晶相;錐光偏振鏡檢法;room-temperature discotic nematic;biaxial nematic phases;board-like;conoscopic;contact preparations.
    Date: 2005
    Issue Date: 2010-01-11 02:38:28 (UTC+8)
    Abstract: 一般盤形向列相所共有的高熔點及小液晶溫度範圍阻礙其實際應用性。本論文第一部份將六炔苯基苯化合物之其中一外圍苯環以雙環取代,以期大幅降低熔點並同時擁有廣大液晶溫度範圍。在分別引入聯苯、苯-環己烯、萘環三種雙環側臂系統後,確可大幅調控其液晶熱性質,並成功的以引入含聯苯側臂合成出第一個具室溫盤形向列液晶相之單一化合物,且具101 oC的液晶溫度範圍。
    系列二化合物主要是開發具穩定向列液晶相的板狀分子,經理論研究預測此向列相有可能具雙軸性,而此特殊液晶性質預期可用來大幅改善現有液晶顯示器之效能。本論文第二部分即參考文獻報導具不穩定向列相四炔苯基苯板狀化合物,將其外圍苯環置換成聯苯以增加液晶核面積並進而增加分子間作用力,以期望穩定其液晶相。此改良確實大幅提升其液晶性質;更重要的是,利用錐光偏振鏡檢法首次證明板形分子可形成雙軸性向列液晶相。另外,利用接觸置備法進一步了解了板狀分子形成之向列相與桿形向列相互容。
    The nematic mesophase from disclike molecules are usually accompanied with high transition temperatures and narrow mesophase ranges that impede its practical applications. In the first part of this thesis, one of the peripheral phenyl ring in hexakis(phenylethynyl)benzene was replaced with a two-ring system, biphenyl, naphthyl, or cyclohex-1-enyl-benzene. In all cases, lower transition temperatures and wider liquid crystal ranges were obtainted. Most importantly, a room-temperature discotic nematic phase was achieved from a single component for the first time.
    It was proposed by theory that molecules with a board-like geometry can potentially exhibit biaxial nematic phases. It is expected that biaxial nematic phases should show significantly shorter switching time than uniaxial nematic phases. In the second part of this thesis, based on the reported board-like 1,2,4,5-tetrakis(phenylethynyl)benzene core showing unstable liquid crystal behaviors, the peripheral phenyls were substituted with biphenyls with stronger intermolecular interactions and hence the nematic phase was stabilized. By conoscopic studies, biaxiality of the resulting nematic phase has been observed for the first time from board-like molecules. Moreover, using contact preparations, the nematic phase from board-like molecules is found to be miscible with calamitic nematic phases.
    Appears in Collections:[Graduate Institute & Department of Chemistry] Thesis

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