C₃-symmetric truxene discotic liquid crystals with mixed ether chains: synthesis, mesomorphism, and self-assembly properties

ABSTRACT

Nine new C₃-symmetric 2,7,12-tris(decanoxy)-3,8,13-tris(alkoxy)truxene discogens were synthesized, and all exhibited only one three-dimensionally ordered hexagonal columnar mesophase with a wide mesogenic temperature range, as characterized by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffractometry. Crucially, as the length of the alkoxy chain increased, the melting points first increased and then decreased, and, at the same time, the temperatures of the clearing point decreased gradually. In addition, these compounds were found to be highly thermally stable, having decomposition temperatures occurring well above 350°C, as determined by thermogravimetric analysis. The self-assembly behaviors in solution were studied using variable-concentration ¹H-NMR, revealing that the truxenes self-aggregated in solution via the π–π facial interactions of the polycyclic aromatic units, and scanning tunneling microscopy results revealed that one of the discotic liquid crystal compounds periodically assembled in a hexagonal geometry at the liquid–solid interface of highly oriented pyrolytic graphite.

KEYWORDS:

• Discotic liquid crystal
• truxene
• hexagonal columnar mesophase
• self-assembly
• scanning tunneling microscopy

Acknowledgments

The support of this research by the National Natural Science Foundation of China (Fund numbers 51973143 and 21772135) is gratefully acknowledged.

Disclosure Statement

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

Supplementary Materials

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Additional information

Funding

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