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    Title: Influences of sterically congested fluoro substituents in hexakis (pheneylethynyl) benzenes on the helical columnar packing
    Other Titles: 無鏈彎曲形分子之構形對液晶性質之影響及引入具立體障礙氟原子對形成扇葉構形對筒型液晶排列螺旋性之影響
    Authors: 郭芷綺;Kuo, Chih-Chi
    Contributors: 淡江大學化學學系碩士班
    徐秀福;Hsu, Hsiu-Fu
    Keywords: 液晶;彎曲型;無鏈;盤形;掌性;掌性放大;螺旋;liquid crystal;bent-rod;chainfree;discotic;chiral induction;chiral amplification;helical swirl
    Date: 2011
    Issue Date: 2011-12-28 18:09:29 (UTC+8)
    Abstract: 本論文分別討論無鏈彎曲形分子之構形對液晶性質之影響及引入具立體障礙氟原子對形成扇葉構形對筒型液晶排列螺旋性之影響。第一部分分別以置換不同的末端官能基與改變其分子側臂的夾角,並佐以單晶結果,探討其無鏈彎曲形分子之構形對液晶性質之影響。第二部分設計單側臂具立體障礙氟原子之六側臂盤狀液晶分子,由氟原子數的增加所增加分子側鏈與分子中心核的平面扭轉角,以形成顯著的類風扇構形,使分子排列與推疊時更為緊密,同時提升了分子排列的次序性。無鏈彎曲形分子之構形對液晶性質之影響及引入具立體障礙氟原子對形成扇葉構形對筒型液晶排列螺旋性之影響。
    The structure-property relationships of liquid crystalline behaviors have been well discussed in the past few decades. In general, the resulting intermolecular cohesion determines the fusion temperature of crystal and flexible chains lower the transition temperatures, thereby stabilizing the mesophases. Nevertheless, there are only a few example on the formation of liquid crystalline phases from mesogens without flexible chains.
    Herein, we investigated the effect of the molecular geometry, especially the dihedral angle and the dipole moment on liquid crystal formation of mesogenic compounds without flexible chains. A series of new bent-rod LCs without flexible chains were studied.
    Induced supramolecular chirality has been observed and reported in columnar LCs when the columns are twisted along the column axis to give helical structures. Hexaynylphenylbenzenes are prochiral due to the possible propeller-like geometry by rotation of sidearms. In this content, one or two lateral fluoro groups were incorporated ortho to ethynyl group onto on peripheral phenyl of hexaynylphenylbenzene. With unique combination of small size and high polarity, fluoro substituent can efficiently modify the mesogenic properties without significantly affecting the molecular geometry. In here, the sterics by the fluoro group(s) is to increase the dihedral angle of the F-attached phenyl and central phenyl to result in a more pronounced propeller geometry. The synthesized fluoro-containing compounds are expected to show higher ordering levels associated to helical disposition along the columns and more efficient chiral amplification is anticipated when these compounds are doped into non-chiral analogs.
    Appears in Collections:[化學學系暨研究所] 學位論文

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