Preparation And Characterization Of New Type Chiral Liquid Crystal Compounds

Chiral liquid crystal, a kind of liquid crystal with chiral group, is one of the hot spot in the research field. Chiral liquid crystal molecules is characterized by an asymmetric carbon atom with chiral center (often with "C*" shown), the molecule itself does not have mirror symmetry. Such kind of liquid crystal molecules form a helical structure due to the presence of chiral centers, and the helical structure makes the liquid crystal have some special optical properties which the generally liquid crystals do not have.In this dissertation, five liquid cyrstalline monomers were synthesized, which include10-(4’-(4-Trifluoromethylbenzoyloxy) biphenyl) sebacic acid (M1), Trifluoromethyl benzoyl biphenyl carboxylic acid (M2),10-(4-((4-ethoxybenzoyl)oxy) phenoxy)-10-oxodecanoic acid (M3),4’-(4-(trifluoromethyl) benzoyloxy) biphenyl acid-2-(10-undecene acyloxy)-propyl ester (M4),4’-(4-(trifluoromethyl) benzoyloxy) biphenyl acid-2-(4-allyloxy benzoyloxy) propyl ester (M5), respectively using M1, M2, M3as the liquid crystalline side arms and isosorbide,1,2-propanediol,1,2,4-butanetriol as the chiral liquid crystalline center to create three seriesnine different chiral liquid crystalline compounds which include10-(4’-(4-trifluoromethyl benzoyl oxy)biphenyl) sebacic acid isosorbide diester (YFG), trifluoromethyl benzoyl diphenyl carboxylic isosorbide diester (YF),10-(4’-(4-ethoxy benzoic acid yl)-phenyl) isosorbide diester of sebacic acid10-bis(4-((4-ethoxybenzoyl)oxy)phenyl)(YYG),10-(4’-(4-trifluoromethyl-benzoic acid yl) biphenyl) sebacic acid propylene glycol diester (BFG), trifluoromethyl benzoyl biphenyl carboxylic acid propylene glycol diester (BF),10-(4’-(4-ethoxy benzoic acid yl)-phenyl) sebacic acid, propylene glycol diester (BYG),10-(4’-(4-trifluoromethyl benzoyl oxy) biphenyl) tri-esters sebacic acid tromethamine (DFG), trifluoromethyl benzoyl Butanetriol three biphenyl carboxylic acid ester (DF),10-(4’-(4-ethoxy benzoic acid yl)-phenyl) sebacic acid triester butanetriol (DYG).There were no reported at home and abroad about M1, M2, M4, M5and the three series of nine different types of chiral liquid crystal compounds.So it is creative in molecular design method.The structures and properties of the obtained liquid crystalline monomers were investigated by FT-IR spectroscopy, XRD, differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Their structure-property relationships were discussed in detail. The optical rotation of monomer M4, M5and the three series of chiral liquid crystal compounds were tested by the Model341Polarimeter of American PE company.Optical analysis shows that M4, M5and BFG,BF, BYQ DFQ DF, DYG are L-optically active substances. YFG, YF, YYG are D-optically active substances.All of the monomers and three series chiral liquid crystal compounds are all meet the molecular design and show liquid crystaline texture. M3and M5are nematic liquid crystals, showing droplet texture and schlieren texture, M1and M2are the smectic liquid crystals, showing fan-shaped pellets texture, M4is cholesteric liquid crystal, showing focal conic texture and broken focal conic texture. YYG, BYG, DYG are cholesteric liquid crystals, all showing a small ball and fingerprint texture. YFG, BFQ DFG are smectic liquid crystal, polarized showing droplet texture and fun-shaped texture. BF and DF are smectic liquid crystals, both of them showed a small ball texture and fun-shaped texture. YF is cholesteric liquid crystal, showing small balls texture and focal conic texture.For chiral liquid crystal compound, the thermal properties and liquid crystal types are impacted by the side arms and the structure of the chiral center. The liquid crystal side-arm with fluoride terminal group and a chiral center attached to the flexible spacer group of a chiral liquid crystal compound will make the melting point rise. When the nematic liquid crystal side arm is connected to the chiral center is generated formed cholesteric liquid crystal. Making smectic liquid crystal connected to the chiral center, most of them are created to smectic liquid crystal, when the chiral center is strong, cholesteric liquid crystal may be generated.