Impact of the proportionation of dialkoxy chain length on the mesophase behaviour of Schiff base/ester liquid crystals; experimental and theoretical study

ABSTRACT

New non-symmetrical homologues series of Schiff base/ester series, 4-alkoxyphenylimino-4ʹ-phenyl-4ʹ’-alkoxybenzoates, have two terminal alkoxy groups (Im/n), were synthesised and investigated for their mesophase behaviour. Where the number of carbon in the alkoxy chains attached to the phenylimino and benzoate moieties named m and n respectively. The newly Schiff base structures were confirmed via elemental analyses IR, and NMR spectroscopy. Mesomorphic properties were investigated by differential scanning calorimetry and polarised light microscopy. All investigated compounds proved to be dimorphic exhibits semictic A and nematic phases with high stability. The present Schiff base groups and the previously prepared 4-alkoxyphenylazo-4ʹ-phenyl-4ʹ’-alkoxybenzoates were compared and results revealed that the replacement the azo linkage by phenylimino group change the mesophase stability and the type of the phase depending up on the length of alkoxy – chain m that attached to the phenylimino mesogenic part. Furthermore, we have performed density functional theory theoretical calculations to confirm the experimental data and the results are in consistent with the experimental investigation.

Graphical abstract

KEYWORDS:

• Liquid crystals
• Schiff base ester
• phase transitions
• nematic phase
• DFT calculations

Acknowledgments

Authors gratefully acknowledge the Deanship of Scientific Research, Taibah University for support of our research group (60333).

Disclosure statement

No potential conflict of interest was reported by the authors.