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

Nine new C-3-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 degrees C, as determined by thermogravimetric analysis. The self-assembly behaviors in solution were studied using variable-concentration H-1-NMR, revealing that the truxenes self-aggregated in solution via the pi-pi 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.

Automated summary

Nine new C-3-symmetric 2,7,12-tris(decanoxy)-3,8,13-tris(alkoxy)truxene discogens were synthesized and exhibited a wide mesogenic temperature range and high thermal stability. The melting and clearing temperatures showed a pattern with the length of the alkoxy chain. In solution, the truxenes self-aggregated through pi-pi facial interactions and formed a hexagonal geometry at the liquid-solid interface.