The effect of orientation of the lateral methyl substituent on the mesophase behaviour of 4-alkoxyphenylazo aryl benzoates

ABSTRACT

Two homologous series of 4-alkoxyphenylazo 4ʹ-(2ʺ- (and 3ʺ-) methyl-) 4ʹ-substituted benzoates (IIn_a–f and IIIn_a–f, six series each) were prepared and investigated. Within each series, the length of the terminal alkoxy group varies among 6, 8, 10 and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changes between the electron-donating CH₃O, CH₃, and the electron-withdrawing Br, NO₂ and CN groups, in addition to the un-substituted analogue, X = H, aiming to investigate the effect of the different orientations of the methyl groups substituted on the central benzene ring, on the mesophase behaviour. The mesomorphic properties were discussed in terms of steric and polarisability effects. The mesophase stability was correlated with the polarisability anisotropy of bonds to the terminal substituent X. Comparative studies were made between the prepared isomers with each other and with the previously investigated laterally neat analogues 4-(4ʹ-alkoxyphenylazo) phenyl 4ʺ-substituted benzoates (In_a–f).

GRAPHICAL ABSTRACT

KEYWORDS:

• phenylazo phenyl benzoates
• mesophase behaviour
• lateral-methyl substitution
• polarisability

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.