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.

Table of contents---------------------------------------------------------------------------------------- 3
List of figures--------------------------------------------------------------------------------------------- 5 
List of tables---------------------------------------------------------------------------------------------- 7 
Abstract---------------------------------------------------------------------------------------------------- 8 
Chapter 1. Introduction------------------------------------------------------------------------------- 9 
1.1. Introduction of Liquid Crystals-------------------------------------------------------------- 9 
1.2. Structure Property Relations-------------------------------------------------------------- 11 
1.3. Types of Liquid Crystals---------------------------------------------------------------------- 12 
1.3.1. Calamitic Liquid Crystals------------------------------------------------------------------ 12 
1.3.2. Discotic Liquid Crystals------------------------------------------------------------------- 14 
1.3.3. Bent Shape Liquid Crystals---------------------------------------------------------------15 
1.4. Motives----------------------------------------------------------------------------------------------16 
Part 1. Structural Factors on Chain-Free Bent-Rod Mesogensmorphism--------16 
Part 2. Influences of Sterically Congested Fluoro Substituents on the Helicity of 
Columnar Supramolecular Structures---------------------------------------------------------- 23 
Chapter 2. Experimental Section---------------------------------------------------------------- 31 
2.1. General Procedures---------------------------------------------------------------------------- 31 
2.2. Experimental---------------------------------------------------------------------------------- 31 
2.3. Synthesis------------------------------------------------------------------------------------------ 33 
Chapter 3. Results and Discussion------------------------------------------------------------ 56 
3.1. Synthetic Strategies--------------------------------------------------------------------------- 56 
Part 1. Structural Factors on Chain-Free Bent-Rod Mesogensmorphism------- 56 
Part 2. Influences of Sterically Congested Fluoro Substituents on the Helicity of
 Columnar Supramolecular Structures-------------------------------------------------------- 60 
3.2. Mesomorphic Behavior----------------------------------------------------------------------- 63 
Part 1. Structural Factors on Chain-Free Bent-Rod Mesogensmorphism------- 63 
Part 2. Influences of Sterically Congested Fluoro Substituents on the Helicity of 
Columnar Supramolecular Structures---------------------------------------------------------- 70 
3.3. X-ray structure analysis of bent-core mesogens----------------------------------- 76 
3.4. Conclusions--------------------------------------------------------------------------------------- 85 
References----------------------------------------------------------------------------------------------- 86 
Appendix I. Crystal Data--------------------------------------------------------------------------- 88 
Appendix II. List of Spectra and DSC-------------------------------------------------------- 95 

List of figures
No
Figures
Page
1Schematic illustration of the solid, liquid crystal, and liquid phase 10
2The typical structural template for a calamitic liquid crystal11
3Schematic representation of the molecular arrangement in (a) nematic, (b) smectic A, (c) smectic C.13
4Schematic representation of the two typical discotic phases.15
5Examples of proposed helical columnar assemblies reported in literature.24
6Polarizing optical micrographs of 10 typical nematic Schlieren texture at 208 °C 67
7Polarizing optical micrographs of 16 a) the droplets of the nematic phase ordering process cooling at 184 °C, and b) typical nematic Schlieren texture at 180 ° 68
8Polarizing optical micrographs of 20 a) the marble texture of nematic phase, and b) typical nematic Schlieren texture on heating process at 256 °C 69
9Polarizing optical micrographs of a) 36 cooling at 177 °C, and b) 37 cooling at 176 °C 72
10Polarizing optical micrographs of 38 cooling at 157 °C 73
11ORTEP diagrams of a) 10c, b) 10, and c) 16, showing the top (normal to the molecular face) with atom labeling and edge views, and 50% probability displacement ellipsoids. 77
12Molecular packing of a) 10c, b) 10, and c) 16, showing opposing and slightly offset dipoles along the long and short axis of the molecule within a unit cell. 79
13Molecular packing of 10c a) along the long axis of the molecules showing the intermolecular hydrogen bonding (–OH…NC–), b) the closest distance between two layers 80
14Molecular packing of 10 in the same plane a) along the long axis of the molecules showing the intermolecular distances between central molecule and periphery molecules, b) the side view of a), and c) the top vies of a).81
15The diagrams showing a) distance between the central molecule to the periphery molecules of 10, and b) the side view of a) 82
16Molecular packing of 16 in the same plane a) along the long axis of the molecules showing the intermolecular distances between central molecule and periphery molecules, b) the side view of a), and c) the top view of a) 84

No
Figures
Page
1Phase behaviors of 1a-1d.17
2Phase behaviors of 2a and 2b 18
3Phase behaviors of compounds from scheme 3 20
4Phase behaviors of 10a to 10c 21
5Phase behaviors of 10a to 10c, 10, 11, 13, 16, 18, and 20 66
6Phase behaviors of 36 to 38, 40, and 41 71
7Phase behaviors of 40, and 41, and the previous research results of 45 74
8The dihedral angles 1, 2, and 3 of 10c, 10, and 16 78

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