Amide And Azo-crown Ether Liquid Crystal Synthesis And Characterization,

The dissertation consists of four parts.1. PrefaceThe basic concept, classification and characterization of liquid crystal, crown ether compound and its application and crown ether liquid crystal and its current research were briefly introduced.2. Synthesis and characterization of amide type crown ether liquid crystalA new kind of amide type crown ether liquid crystal was synthesized on the base of molecular design, which can be divided into four series, sixteen compounds according to the end alkoxy group, crown ether ring and configuration of the compound. The chemical structures of them are as follows: Series I and IICis-4,4 -bis{4 -[4 -(p-alkoxylbiphenyl)-carbonyloxy]benzamido}dibenzo-14-crown-4(131) Trans-4,4-bis{4 -[4 -(p-alkoxylbiphenyl)-carbonyloxy]benzamido}dibenzo-14-crown-4(13II)13I,13II, 14I, and 14II A: R=n-C6H13 ; B: R=n-C8H17; C: R=n-C10H21; D: R=n-C12H253. Synthesis and characterization of azo type crown ether liquid crystalUsing cis(trans)-diaminodibenzo-14-crown-4 and cis(trans)-diaminodibenzo-18-crown-6 as raw materials, a new kind of azo type crown ether liquid crystal was synthesized through diazotization and coupling reactions on the base of molecular design, which can be divided into four series, sixteen compounds according to the end alkoxy group, crown ether ring and configuration of the compound. The chemical structures of them are as follows:Series IV and V :Cis-4,4 -bis[4 -(n-alkoxylbiphenyl)-4-carboxylphenylazo]dibenzo-14-crown-4 (6I)Trans-4,4 -bis[4 -(n-alkoxylbiphenyl)-4-carboxylphenylazo]dibenzo-14-crown-4(6 II)4. Results and discussionsThe structures of intermediates and final compounds were confirmed by means of IR, UV-Vis, H NMR, Mass spectroscopy and Elemental Analysis. The polarizing optical microscopy, DSC, X-ray scattering were applied to identify the mesophase of the compounds. The influence of end alkoxy group, crown ether ring and configuration of the compound on the liquid crystalline behavior have been researched and some rules were generalized. It has been found for the first time that amide type crown ether liquid crystal containing dibenzo-14-crown-4 can form chiral smectic C phase and azo type crown ether liquid crystal can form inversion walls schlieren texture with the increase of end alkoxy group.Experimental results have shown that: (l)Amide type crown ether liquid crystal compounds 3,5,13,14 and azo type crown etherliquid crystal compounds 3,6,7 have thermotropic liquid crystal properties. (2)0nce heated to their own melting temperature, all the compounds above will go into liquid crystal phase. The typical threaded texture, Schlieren texture, ball granul texture, inversion walls schlieren texture of nematic phase and fan texture ,broken focal-conies texture,mosaic texture, sanded texture, lined 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 roomtemperature upon quenching from the melt. (4)A11 the compounds in their liquid crystal state can be easily oriented in the direction ofexternal force.(5)For amide type crown ether liquid crystal compounds 13 and 14, both melting point(Tm) and isotropization temperature(Tj) decrease and smectic phase length increases with the increase of carbon numbers of the end alkoxy group; Tm and T, of compounds 14 I are higher than those of 13 I ; Tm and Tj of compounds 14II are higher than those of 13II; Tm and Ti of compounds 13II and 14II having trans-configuration are higher than those of their corresponding cis-configuration compounds 13 I and 14 I .The Tm of amide type crown ether liquid crystal compounds is relatively high due to the formation of intermolecular hydrogen bond.For azo type crown ether liquid crystal compounds 6 and 7, both Tm and Tj decrease with the increase of carbon numbers of the end alkoxy group and the temperature range of liquid crystal phase is relatively wide; Tm and Tj of compounds 7 I are higher than those of 6 I ; Tm and Tj of compounds 7II a...