Effect of orientation of lateral methyl substituent on the thermal behaviour of the mesophase in binary systems of 4-substituted phenyl 4ʹ-(4”-alkoxy phenylazo) benzoates

Several binary systems made from two laterally substituted azo/ester isomers, namely 2";- (and 3";-) methyl-4-substituted phenyl 4'-(4";-alkoxyphenylazo) benzoates, where the length of the terminal alkoxy group = 8 and 16 carbons, while the other terminal substituent, X, varies b...

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Bibliographic Details
Published in:Liquid crystals 2018-06, Vol.45 (8), p.1177-1185
Main Authors: Saad, Gamal R., Ahmed, Nagwa H.S., Fahmi, Abdelgawad A., Naoum, Magdi M.
Format: Article
Language:English
Subjects:
Benzoates
Binary systems
Calorimetry
Eutectic composition
Isomers
Mesophase
Orientation effects
Phase diagrams
Substitutes
Temperature dependence
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Summary:Several binary systems made from two laterally substituted azo/ester isomers, namely 2";- (and 3";-) methyl-4-substituted phenyl 4'-(4";-alkoxyphenylazo) benzoates, where the length of the terminal alkoxy group = 8 and 16 carbons, while the other terminal substituent, X, varies between CH3O, CH3, H, Br and CN groups, were investigated using differential scanning calorimetry (DSC) and phases identified by polarised light microscope (PLM). For the sake of comparison, two another binary systems made from 2";- (or 3";-) methyl-4-substituted phenyl 4'-(4";-alkoxyphenylazo) benzoates (n = 8 and X = CH3) each was mixed with its laterally neat analogue and similarly investigated. Results were discussed on the basis of constructed phase diagrams whereby various mesomorphic properties were observed dependent on X, n, and position of the lateral methyl group. In most of the cases, the mixtures exhibited eutectic compositions, while linear or nearly linear nematic and smectic A-composition temperature dependence were observed.
ISSN:0267-8292
1366-5855
DOI:10.1080/02678292.2017.1417503