Synthesis and mesomorphic behaviour of new disulphide bridge 4-n-alkoxybenzylidine-4′-bromoaniline

Abstract

Six members of homologues series of the liquid crystal dimers, 4-n-alkoxybenzylidine-4′-bromoaniline disulphides, which contain a sulphur–sulphur (S–S) link in the flexible spacer have been synthesised and their liquid crystalline properties were characterised. The dimers possess a general formulation in which a S–S group situated between two identical bromo-substituted aromatic imines have bonded, respectively, to S atom through the methylene unit of –(CH₂)_n– in which n denotes the number of carbon atoms. The number of carbon atoms in the spacers were varied following ascending order from 3 to 8. The dimers with a shorter spacer (n = 3 and 4) displayed nematic phase as well as smectic phase. The higher homologues in which n = 5–8 exhibited smectogens. The odd–even effect can be ascribed to the torsion angle of S–S linkage.

Keywords:

• liquid crystal dimers
• disulphide linkage
• flexible spacer
• imine-based
• torsion angle

Acknowledgements

The author (G.Y. Yeap) would like to thank Universiti Sains Malaysia for providing the research facilities.