Synthesis and characterization of ethyl cellulose based liquid crystals containing azobenzene moieties

Monira Lizu (2009) Synthesis and characterization of ethyl cellulose based liquid crystals containing azobenzene moieties. Masters thesis, Universiti Malaysia Sabah.


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The liquid crystal state is a well known state of matter, whose order is between the crystal solid and isotropic liquid states and characterised by having long-range orientational order and possible partial positional order. The main objective of this study is to synthesize novel liquid crystals compounds containing azo (-N=N-) chromophores linked with cellulose (ethoxy content 48 wt %) which is very popular as a naturally occurring polymer, it is abundant, renewable, biodegradable and highly functional. For accomplishment of synthesis part, acid compounds namely 4-(4-hexyloxy-phenylazo )benzoic acid, 4-( 4-decyloxy-phenylazo )benzoic acid, 4-(4-allyloxyphenylazo )benzoic acid and 4-[4-( 4-Allyloxybutyloxy)phenylazo]benzoic acid were esterified with ethyl cellulose using of N,N'-Dicyclohexylcarbodiimide (DCC) and 4-Dimethylaminopyridine (DMAP). Thus final compounds namely ethyl (β-D-glucopyranoside [4-(4-hexyloxy-phenylazo)benzoate] (EC-AZQ-4), ethyl (β-D- glucopyranoside [4-(4-decyloxy-phenylazo) benzoate] (EC-AZO-C�₀)' ethyl (β-D- glucopyranoside [4-(4-allyloxyphenylazo)benzoate] (EC-AZO-alkene) and Ethyl (β-D- glucopyranoside 4-[4-( 4 Allyloxybutyloxy)phenylazo]benzoate] (EC-AZQ-4-alkene) were obtained. The molecular structures and characteristics of the intermediates and target compound were further confirmed by spectroscopic methods. The structure of intermediate and target compound was confirmed by FTIR and NMR spectroscopy. The phase transitions temperatures were determined by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Textural identification of phase structures using POM indicated that compound EC-AZO-C₆ showed a typical texture for columnar phase at 100�C and similar compound EC-AZO-C�₀ with long alkyl chain showed smecticA phase at 120°C. Compound EC-AZO- alkene and EC-AZO-C₆-alkene containing the polymerisable double bond at the terminal position which showed only crystalline phase. For photoisomerisation study, UV-Vis absorption was carried out of azobenzene (EC-AZO-C₆, EC-AZO-C�₀, EC-AZO-alkene and EC-AZO-C₆-alkene) containing liquid crystals in solution state. The absorption spectrum of the azobenzene groups displays a high-intensity π-π✶• transition at about 364 nm and a low intensity n-π✶ transition at around 468 nm for these compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to ethyl cellulose containing liquid crystals for the creation of optical data storage devices.

Item Type: Thesis (Masters)
Uncontrolled Keywords: liquid crystal, liquid Crystal Mesophase, Polymer Liquid Crystals (PLC), Ethyl Cellulose, spectrum analysis
Subjects: Q Science > QD Chemistry
Divisions: SCHOOL > School of Science and Technology
Date Deposited: 14 Jul 2014 02:09
Last Modified: 30 Oct 2017 02:07

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