| The dissertation consists of four parts.1. PrefaceThe basic concept, classification and characterization of liquid crystal, crown ether compounds and their application, liquid crystalline crown ether and current research were introduced briefly.2. Synthesis and characterization of azo type liquid crystalline crown ether ligandsUsing cis(trara)-diaminodibenzo-18-crown-6 as raw materials, a novel kind of azo type liquid crystalline crown ether ligand was synthesized through diazotization and coupling reactions on the base of molecular design, which can be divided into two series, eight compounds according to the end alkoxy group and configuration of the compound. The chemical structures of them are shown as follows:Series I and IICz's-4,4 - bis[4 -(n-alkoxylbiphenyl)-4-carboxylphenylazo]dibenzo-l 8-crown-6(8 I)Trans-4,4 -bis[4 -(n-alkoxylbiphenyl)-4-carboxylphenylazo]dibenzo-18-crown-6(8 II)3. Synthesis and characterization of azo type liquid crystalline crown ether complexes8 I A~8 I D and 8II A~8IID used as ligands, complex with K+, Pd2+, La3+and Eu3+ ion respectively, a new kind of azo type liquid crystalline crown ether complexes was therefore synthesized, which can be divided into eight series, 32 complexes according to the end alkoxy group, configuration and metal ion of the compound.4. ConclusionThe structures of the ligands and their complexes were characterized ed by means of IR, UV-Vis, 1H NMR, Elemental Analysis, fluorescence and atomic absorption method. The polarizing optical microscopy, DSC and WAXD were applied to identify the mesophase of the compounds.The synthesis procedure is optimized and improved. Some key techniques and thorny problems about the chose of solvents , the purification and separation of products are solved.The influence of end alkoxy group, configuration and eomplexation of the compound on the liquid crystalline behavior have been invested and some rules were generalized. It has been found for the first time that azo type crown ether liquid crystal can form inversion walls schlieren texture. Experimental results have shown that:1) Compounds 3,81, 8II and complexes of 8 I and 8II have thermotropic liquid crystal properties.2) Once heated to their own melting temperature, all the compounds obtained above will gointo liquid crystal phase. The typical Schlieren texture, inversion walls schlieren texture of nematic phase and broken focal-conies texture, mosaic texture and grating texture of smectic phase can be observed.3) The liquid crystal texture of all the compounds can be kept for a long time at room temperature upon quenching. In their liquid crystal state, all the compounds can be easily oriented in the direction of external force.4) All the complexes are nonelectrolytes, the molar conductivity is very small. The molarconductivities of cis- configuration complexes are higher than those of trans- complexes, and decrease with the increasing of carbon numbers in the end alkoxy group in the same configuration series of complexes.5) All the ligands and complexes have fluorescent properties. After eomplexation, the position of the most intense peak in the fluorescence excitation spectrum shift to longer wavelengths, the emission maximum, however, shifts towards shorter wavelengths.6) For ligands and their complexes of same configuration and same series, both Tm and T, decrease with the increase of carbon numbers in the end alkoxy group and the temperature range of smectic phase increase, whereas the temperature range of nematic phase decrease. Tm and T( of compounds having trans-configuration are higher than those of their corresponding cw-configuration compounds.7) Tm of complexes is smaller than their ligands (except trans- configuration complexes ofpotassium, lanthanum and europium), in the same time, Ti of complexes are higher than those of their ligands. So the liquid crystal phase length becomes broader after eomplexation.8) The liquid crystalline phase of ligands can be changed through complexation with metalion. |
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