Room temperature nematic liquid crystals: Synthesis and characterisation of pentabromophenol and cyanobiphenyl derived rod-shaped molecules

Abstract

Calamitic molecules consisting of pentabromophenol tethered to cyanobiphenyl via a flexible alkyl chain were synthesised and characterised for their mesomorphic properties. New chemical structures differing in the length of the spacer (6a–f) were confirmed by FT-IR, 1H-NMR and 13C-NMR spectroscopies, and by elemental analysis. Compounds having six, eight, nine and ten methylene units in the spacer show room-temperature nematic liquid crystalline phases and the other derivatives are soft solids. The mesomorphic behaviour and thermal stability of all compounds have been investigated by polarised optical microscopy, differential scanning calorimetry and thermal gravimetric analysis, respectively.