Azo substituted V-shaped liquid crystalline compounds: synthesis and mesophase characterisation

Abstract

The first examples of V-shaped liquid crystalline materials made of non-symmetrical molecules are reported. They belong to a homologous series of azo substituted compounds, wherein the two arms attached to the 1,2-positions of the benzene ring are different. The new compounds are characterised by the spectroscopic methods. The liquid crystalline properties are investigated using polarising optical microscopy, differential scanning calorimetry and X-ray diffraction studies. All the compounds synthesised here are found to be liquid crystalline. They exhibit nematic and smectic A mesophases, which are uniaxial in nature. The preliminary qualitative experiments showed that the compounds are photosensitive. Based on the X-ray results, the molecular arrangement of these compounds in their mesophases is illustrated. A relationship between molecular structures to mesomorphic properties in such systems has also been predicted.

Keywords:

• azo compound
• liquid crystal
• photosensitive
• V-shape
• X-ray
• nematic
• smectic

Acknowledgements

We are grateful to Prof. V.A. Raghunathan and Dr Arun Roy for useful discussions during the X-ray study.