Synthesis, Characterisation And Determination Of Mesophase Transition Of Cyclotriphosphazene Derivatives With Azo Linking Unit
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Date
2017-07
Authors
Loh, Miyeko Lotus Leh Ching
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
A series of intermediates were synthesised via azo coupling reactions to give the alkylated compounds with one azo linking unit, 2a-c and with two azo linking
units, 5a-c. These intermediates were subjected to further monosubstitution and
hexasubstitution reactions with cyclotriphosphazene to produce a series of final compounds 7a-f. These compounds were characterised using FT-IR (Fourier
Transform Infrared), 1D and 2D NMR (Nuclear Magnetic Resonance) spectroscopy
and CHN elemental analysis. Intermediates 2d-f and 4a-c were found to be mesogenic with nematic and smectic phases, as determined under the POM (Polarised Optical Microscopy). The endotherms obtained from the DSC
(Differential Scanning Calorimetry) showed the respective phase transitions of
crystal-mesophase, mesophase-mesophase if any, and mesophase-isotropic phases during the heating cycle; and vice versa during the cooling cycle. The influence of
terminal groups and linking groups on mesogenic properties was discussed.
Smectogenicity was found to be enhanced with increasing alkoxy chain length.
Mono- and hexa-substituted compounds 7a-f were found to be non-mesogenic. It
was concluded that the introduction of non-mesogenic side arms resulted in the lack
of liquid crystalline properties in 7a-f.
Description
Keywords
Determination of mesophase transition of cyclotriphosphazene , derivatives with azo linking unit