Preparation of fluoro-substituted liquid crystals containing azobenzene moieties

Sia, Sung Kiong (2007) Preparation of fluoro-substituted liquid crystals containing azobenzene moieties. Universiti Malaysia Sabah. (Unpublished)


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The objective of this study was to synthesize liquid crystals compounds with fluorosubstituted and containing azobenzene moieties. The starting material, ethyl-4- aminobenzoate was undergone diazonium coupling reaction with 2-fluorophenol to give 4-(4-hydroxy-3-fluorophenylazo) ethyl benzoate. The second step of the reaction was Williamson ether synthesis on the diazonium salt to give 4-(4-hexyloxy-3- fluorophenylazo) ethyl benzoate. This compound was then hydrolyzed to yield 4-(4- hexyloxy-3-fluorophenylazo) benzoic acid. The final step was the esterification reaction of carboxylic acid with resorcinol, DCC and DMAP. The final compound formed was a bent-shape liquid crystal, 1 ,3-phenylene-bis-[ 4-( 4-hexyloxy-3-fluorophenylazo) benzoate]. The structure and characteristic of the intermediates and final compound were confirmed by spectroscopic analysis with FT-IR, ¹H NMR and DSC. FT-IR spectrum for intermediate and final compound indicated the presence of functional groups included alkyl, aryl, ester, ether, carboxylic acid, amines etc. ¹H NMR spectrum showed the molecular structure of the final compound but with some impurities. Thermogram DSC showed the phase transition temperature of crystalline to mesophase (Cr-M) at 62.68°C and mesophase to isotropic (M-I) at 138.60°C in endothermic while in exothermic isotropic to measophase (I-M) and mesophase to crystal (M-Cr) phase appeared at 130.34°C and 59.90°C, respectively. These analyses had showed that the compound synthesized were liquid crystals but a the pure compound as projected.

Item Type: Academic Exercise
Uncontrolled Keywords: liquid crystal, azobenzene moieties, reaction, fluoro-substituted, mesophase, phase transition temperature, FT-IR spectrum
Subjects: T Technology > TP Chemical technology
Divisions: SCHOOL > School of Science and Technology
Date Deposited: 24 Mar 2014 06:25
Last Modified: 13 Oct 2017 01:31

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