Hockey stick-shaped azo compounds: effect of linkage groups and their direction of linking on mesomorphic properties

Abstract

Several new hockey stick-shaped azo compounds are designed and synthesised with an aim to study the effect of different types of linkages and their direction of linking on the mesomorphic properties in such systems. The new compounds synthesised are characterised by spectroscopic methods. The liquid crystalline properties are investigated using polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. They exhibited a variety of mesophases such as nematic (N), smectic A (SmA), anticlinic smectic C (SmC_a), B₁, etc. We found that the direction of linkage groups has a major effect on the mesomorphic properties when compared to the effect of different types of linkage groups. We observed a reversible photo-switching phenomenon of these compounds in their solution UV–vis spectra.

Keywords:

• hockey stick shape
• azo compound
• anticlinic smectic C
• smectic A
• nematic
• photo-switching

Acknowledgement

We sincerely thank Dr Arun Roy for his useful discussions during mesophase characterisation.