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

ABSTRACT

Several binary systems made from two laterally substituted azo/ester isomers, namely 2ʺ- (and 3ʺ-) methyl-4-substituted phenyl 4ʹ-(4ʺ-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 2ʺ- (or 3ʺ-) methyl-4-substituted phenyl 4ʹ-(4ʺ-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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Phenylazo phenyl benzoates
• lateral-methyl substitution
• mesophase behaviour
• binary phase diagrams

Disclosure statement

No potential conflict of interest was reported by the authors.