| Chiral liquid crystals (CLC) have attracted much interest because of their unique optical and electrical properties which due to their helical structures. Star-shaped crystal is a new type of liquid crystal which is different from the traditional liquid crystal, It has theoretical significance and application value because of its unique spatial configuration and rheological properties.In this dissertation, eight liquid crystalline monomers have been successfully synthesized, which include 4-(undec-10-enoyloxy) benzoic acid (M1),4’-(undeca-1,10-dien-2-ylperoxy)-[1,1’-biphenyl]-4-carboxylic acid (M2),4’-((4-(buta-2,3-dien-1-yloxy) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic acid (M3),6-(4-((4-ethoxybenzoyl) oxy) phenoxy)-6-oxohexanoic acid (M4),4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic acid (M5),2-hydroxypropyl 4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylate (M6),4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic isosorbide ester (M7),4’-((4-(buta-2,3-dien-1-yloxy) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic Cholesterol ester (Ms).Two series of multi-arm liquid crystals (LCs) have been successfully synthesized by using 1,2,4-butanetriol as the chiral core and M3, M4 and M5 as liquid crystal arms, respectively. The flowing multi-arm LCs were synthesized by using M4 and Ms as liquid crystal arms:Tri{4’-((4-(trifluoromethyl)benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid} butanetriol ester (DFJO), Di{4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic acid}-Mono{6-(4-((4-ethoxybenzoyl) oxy) phenoxy)-6-oxohexanoic acid} butanetriol ester (DFJ1), Mono{4’-((4-(trifluoromethyl) benzoyl) oxy) [1,1-biphenyl]-4-carboxylic acid}-Di{6-(4-((4-ethoxybenzoyl) oxy) phenoxy)-6-oxohexanoic acid} butanetriol ester (DFJ2), Tri{6-(4-((4-ethoxybenzoyl) oxy) phenoxy)-6-oxohexanoic acid} butanetriol ester(DFJ3). The fllowing multi-arm LCs were synthesized by using M3 and M5 as liquid crystal arms:Tri{4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic acid} butanetriol ester (DFXO), Di{4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylic acid}-Mono{4’-((4-(buta-2,3-dien-1-yloxy) benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid} butanetriol ester (DFX1), Mono{4’-((4-(trifluoromethyl)benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylicacid}-Di{4’-((4-(buta-2,3-dien-1-yloxy)benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid} butanetriol ester (DFX2), Tri{4’-((4-(buta-2,3-dien-1-yloxy) benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid} butanetriol ester (DFX3).M6 was synthesized by using 1,2-propanediol and Ms. The following LCs were synthesized by using M6 and M1, M2 and M3, respectively. They are{4-(undec-10 enoyloxy) benzoic acid}-{4’-((4-(trifluoromethyl) benzoyl)oxy)-[1,1’-biphenyl] 4-carboxylic acid} propanediol diester (BFB1),{4’-(undeca-1,10-dien-2-ylperoxy)-[1,1’-biphenyl]-4-carboxylicacid}-{4’-((4-(trifluoromethyl)benzoyl)oxy)-[1,1’-biphenyl]-4-carboxy-licacid} propanediol diester (BFB2),{4’-((4-(buta-2,3-dien-1-yloxy) benzoyl) oxy)-[1,1’-biphenyl]-4-carboxylicacid}-{4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1-biphenyl]-4-carboxylic acid} propanediol diester (BFB3).M7 was synthesized by using isosorbide and M5. The following LCs were synthesized by using M7 and M1, M2 and M3, respectively. They are{ 4-(undec-10-enoyloxy) benzoic acid} {4’-((4-(trifluoromethyl) benzoyl) oxy)-[1,1-biphenyl]-4-carboxylic acid} isosorbide diester (YFB1),{4’-(undeca-1,10-dien-2-ylperoxy)-[1,1’-biphenyl]-4-carboxylic acid}-{4’-((4-(trifluoromethyl) benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid} isosorbide diester (YFB2),{4’-((4-(buta-2,3-dien-1-yloxy) benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid}-{4’-((4-(trifluoromethyl) benzoyl)oxy)-[1,1’-biphenyl]-4-carboxylic acid} isosorbide diester (YFB3).The structures and properties of the obtained liquid crystalline monomers and multi-arms crystal compounds were investigated by FT-IR spectroscopy, differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), XRD. Their structure-property relationships were discussed in detail. The optical rotation of monomers M6, M7, Ms and the three series of chiral liquid crystal compounds were characterized by theW22-2S-2SS Polarimeter of Shanghai.All the synthesized LCs are all consistent with the molecular design and show liquid crystal properties.M1 and M5 are smectic B LCs; M2 is smectic C LCs; M3 and M4 are nematic LCs; M6 displays chiral smectic C and nematic LC properties in heating cycle and nematic LC properites in cooling cycle. M7 and Ms are chiral cholesteric LCs.Two series of multi-arms LCs synthesized by using 1,2,4-butanetriol as the chiral core all display thermotropic and bivariant LC properties. For the series of DFJ, DFJO and DFJ3 are chiral smectic C and cholesteric LCs, respectively. DFJ1 and DFJ2 are nematic LCs. For the series of DFX, DFXO and DFX2 are chiral smectic C and cholesteric LCs, respectively. DFX I and DFX2 all display chiral smectic A and cholesteric LCs properties.The research results of D series containing chiral core show that multi-arm liquid crystals which the structures of the LC arms are same or similar are prone to display chiral properties. The multi-arms LCs are difficult to exhibit chiral properties when the structures of their LC arms are different.The series of miktoarm LCs B by using 1,2-propanediol as the chiral core are thermotropic and bivariant chiral LCs. BFB1 is chiral smectic C LC; BFB2 is chiral smectic A LC; BFB3 is cholesteric LC.The series of miktoarm LCs Y by using isosorbide as the chiral core are thermotropic and bivariant chiral LCs. YFB1 and YFB3 are cholesteric LCs; YFB2 display chiral smectic A and cholesteric LC properties.The research results of B and Y series show that the LCs are prone to display chorestreic properties when the optically active of their chiral core is stronger. The LCs are prone to exhibit smectic properties when the optically active of their chiral core is weaker and the flexible chain of terminal group is longer. |
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