EFFECT OF HETEROATOMS IN THE SIDE-CHAINS OF DISK-LIKE MOLECULES ON THE FORMATION OF DISCOTIC LIQUID-CRYSTALLINE PHASES

Incorportion of oxygen and sulfur atoms into the side chains of discotic liquid crystals generally results in a depression of both the crystal to discotic and discotic to isotropic transition temperatures relative to the n-alkyl analogue. In contrast, replacement of the methylenes in side-chain positions 4 of 2,3,6,7,10,11-hexakis(alkanoyloxy)triphenylenes increases the clearing (M-I) temperature from 120 to 200-degrees-C. This effect is specific for sulfur substitution, to the triphenylene series, and to the 4-position. It is not expected, based on a simple model for discotic-phase formation.