Alkyl acid hydrazide-containing liquid crystalline triphenylenedicarboxyimides

ABSTRACT

Seven hydrazide-containing triphenylenedicarboxyimides (TDIs) bearing four β-octyloxy side chains and one alkyl acid amide group at the imide nitrogen have been synthesised. These TDIs exhibit enantiotropic mesophases with broad mesomorphic temperature ranges and high clearing temperatures between 258°C and 318°C. Notably, TDI-NHCO-C₄H₉ with a n-butyl side chain exhibits a wide mesomorphic temperature range of over 300°C extending from below room temperature to 303°C. In contrast, its branched isomer TDI-NHCO-C(CH₃)₃ carrying a bulky tert-butyl chain displays a hexagonal columnar mesophase between 105°C and 318°C with the highest clearing temperature within the series, indicating that branching leads to a stabilisation of the mesophase. On the other hand, the approximately 83°C increase in the clearing temperature of hydrazide TDI-NHCO-C₄H₉ relative to imide TDI-C₄H₉ lacking the hydrazide function indicates a significant enhancement of mesophase stability upon introducing the hydrazide functional group. However, variable-temperature infrared studies revealed the presence of weaker hydrogen bonds below the clearing temperature, which do not significantly contribute to the stabilisation of the columnar mesophase. Instead, the primary stabilisation mechanism is attributed to the synergistic effect of π–π interactions and dipole–dipole interactions.

GRAPHICAL ABSTRACT

KEYWORDS:

• Columnar phase
• discotic liquid crystal
• hydrogen bond
• triphenylenedicarboxyimide
• hydrazide-functionalised

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/02678292.2023.2292624.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [21772135, 21871195 and 51973143].