Anthraquinone-based discotic liquid crystals: new monomers and dimers

Abstract

We report the design and synthesis of six new series of anthraquinone-based monomers and dimers and studies on their structure–property relationship with respect to their liquid crystalline properties. The chemical structures of these newly synthesised compounds are characterised by infrared (IR), nuclear magnetic resonance (NMR) and mass spectroscopy. The liquid crystalline properties are investigated using polarising optical microscopy, differential scanning calorimetry and X-ray diffraction studies. Most of the compounds synthesised here are found to be liquid crystalline. In many cases, the mesophases stabilised up to room temperature. They exhibit a variety of mesophases, viz., Col_h and D_L, in addition to an unidentified mesophase, M_x. We have made an effort to propose a molecular model in the discotic lamellar phase of one of the dimer compounds based on the X-ray data obtained.

Keywords:

• anthraquinone
• discotic liquid crystal
• monomer
• dimer
• discotic lamellar

Acknowledgement

We thank Professor V.A. Raghunathan, for his help during X-ray measurements. Thanks are also due to Mr. Sanjay K. Varshney, for running the mass spectra and for his help while synthesising compound 2.