Polarizing Microscopy of a Chiral Discotic

Abstract

We studied a liquid crystalline compound of disk-like molecules that has a mesophase in the temperature range 104–180°C. The compound exhibits schlieren textures typical to the discoidal nematic phase within this temperature range. Chemical modification of this compound with chiral groups allowed to synthesize a chiral discotic. Incorporating the chiral discotic as a dopant in the discotic compound we produced chiral structures. In the mixtures of chiral and non-chiral discotic, we observed textures typical to rod-like cholesterics: oily streaks, fingerprint textures, and Cano-Grandjean lines in wedge cells. The induced cholesteric pitch was estimated from fingerprint textures. We induced chiral structures with pitch between 10μm and 40μm for the concentration range 1–7 weight % of chiral discotic.

Key Words:

• discotic liquid crystal
• chiral discotic
• liquid crystalline textures