A series of new unsymmetrical triphenylene discotic liquid crystals containing m-dinitrobenzoate moiety, 2-(3,5-dinitrobenzoyloxy)-3,6,7,10,11-pentaalkoxy triphenylene derivatives (3a～3f) were prepared. Their mesomorphic properties were studied with polarizing optical microscopy and differential scanning calorimetry. The results showed that these compounds exhibit high clearing points, stable columnar mesophases and wide mesophase ranges. It was discovered that, as the length of soft chains increase, the melting points and clearing points of these compounds decreased, but the order of hexagonal columnar mesophases had no obvious change. The mesomorphism of compounds 3a～3f was compared and contrasted with other three series of compounds, 2-benzoyloxy-3,6,7,10,11-pentaalkoxytriphenylene (4a～4f), 2-ferrocenylcarbonyloxy-3,6,7,10,11-pentaalkoxytriphenylene (5a～5f), and 2,3,6,7,10,11-hexaalkoxytriphenylene (6a～6f). The influences of ester substituent, electron deficient group, and the size of substituent on the mesomorphism were discussed. The results confirmed the notion that small change in chemical structures of discotic liquid crystals could cause a big difference in their mesomorphism.

Key words: triphenylene, discotic liquid crystal, columnar mesophase, unsymmetrical substitution, m-dinitrobenzoate