Synthesis and liquid crystalline behavior of hydrazide-functionalized triphenylenedicarboxyimides

Seven hydrazide-functionalised triphenylenedicarboxyimides (TDIs) which contain a benzamide group bearing different polar substitutes connected to the imide N atom have been studied with the aim to establish the effect of hydrogen bonding and polar substituents on their mesomorphism properties. Six of seven hydrazides each form two types of hexagonal columnar liquid crystalline (LC) phase, including a low-temperature Colho phase and a high-temperature Colhd phase, which were confirmed by characteristic pseudo focal conic fan-shaped textures and XRD measurements. Temperature-dependent FT-IR studies indicated that hydrogen bonding is not strong enough to exist in the LC phases of these hydrazides and disfavours the stabilisation of the columnar mesophase. Nevertheless, dipole–dipole effects were found to favour the mesophase stabilities of these compounds, and the position of the lateral substituent attached to the end benzene ring has a significant impact on the self-assembly by affecting the overall dipole moment.