Synthesis of V-shaped liquid crystals containing azo chromophores

Tan, Jaclyn Cheeh Fen (2008) Synthesis of V-shaped liquid crystals containing azo chromophores. Universiti Malaysia Sabah. (Unpublished)

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Abstract

The main objective of this study was to synthesize V-shaped liquid crystals materials containing azo chromophores. The starting material, methyl-4-aminobenzoate, was used to undergo diazonium salt coupling reaction with phenol to obtain methyl-4-(4- hydroxyphenylazo)benzoate. The next step of the reaction was Williamson's ether synthesis, whereby hexadecyl bromide was added to the diazonium salt to give methyl-4-(4-hexadecyloxyphenylazo)benzoate. The ester functional group (benzoate) of this compound was then hydrolyzed with sodium hydroxide, yielding 4-(4- hexadecyloxyphenylazo)benzoic acid. Lastly, the benzoic acid was reacted with catechol in the presence of DCC and DMAP for the Fischer esterification reaction. As the result, 15.78 % of yellow V-shaped liquid crystals, 1,2-phenylene-bis[4-(4- hexadecyloxyphenylazo)benzoate], with a melting point ranging from 198 - 202 °C was obtained. The molecular structures and characteristics of the intermediates and target compound were further confirmed by spectroscopic methods and thermal analysis including FT-IR, ¹H-NMR and DSC. From the FT-IR spectra of all intermediates and the final compound, the functional groups that present in each compound were shown and were identified as alkyl, aryl, ether, ester, carboxylic acid, etc. for each spectrum. 'H-NMR spectrum of the final compound showed the types of protons as in the projected molecular structure of the V-shaped target molecule with the presence of some impurities. DSC thermogram showed the phase transition temperatures of crystalline to isotropic (Cr-I) at 198.39 °C for endothermic while for exothermic, isotropic to crystal (I-Cr) phase appeared at 148.53 °C. However, from the DSC thermogram analysis, the synthesized compound did not show liquid crystal mesophase but crystalline phase.

Item Type: Academic Exercise
Uncontrolled Keywords: synthesiz, V-shaped, liquid crystal, azo chromophores, FT-IR, DSC thermogram, crystalline phase
Subjects: T Technology > TP Chemical technology
Divisions: SCHOOL > School of Science and Technology
Depositing User: MDM SITI AZIZAH IDRIS
Date Deposited: 25 Apr 2014 00:51
Last Modified: 13 Oct 2017 03:12
URI: http://eprints.ums.edu.my/id/eprint/8801

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