m -C≡≡ C-] 2 , 8(m), (m = 1, 3) by Eglinton coupling reaction. The thermotropic liquid crystal properties were studied by differential scanning calorimetry and polarized optical microscopy. The results are showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers; dimers 3(n) (n = 5-8) and 6 had glass columnar phase, and no crystallization was observed above −50℃ for all the triphenylene dimers; compared with 3(6), 6 showed higher molecular symmetry, more stable columnar mesophase and wider mesophase range. The connecting group, length and rigidity of spacer had important influence on the mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers.triphenylene, discotic liquid crystal, Eglinton coupling reaction, liquid crystal dimer, glass columnar phase Liquid crystal dimers are a type of molecule which contain two identical or different mesogenic groups linked via a spacer. Their physical properties are different from those of conventional low molecular mass liquid crystals. They show a variety of mesophases [1][2][3][4][5][6] and some of liquid crystal dimers display properties of polymers, such as glass transition behavior [7][8][9] . So they can serve as ideal model compounds in liquid crystal polymer investigation and have received considerable attention. Rod-like liquid crystal dimers have been well studied and their structure-property relationships have been elucidated [10] . By contrast, discotic liquid crystals (DLCs) have comparatively short history. Thus, further exploration of the synthesis, characterization and structure-property relationships of DLC dimers, oligomers and polymers is necessary.Triphenylene derivatives are important family members of DLCs. They can self-assemble into highly ordered hexagonal columnar (Col ho ) mesophase and possess high mobility of charges and energy [11] . Moreover, triphenylene DLCs can be easily synthesized and purified, showing plenty of structural variation and fine thermal and chemical stability [12,13] . They have been applied as one-dimensional conductors [14] , photoconductors [15] , and light-emitting diodes [16] . In recent years, triphenylene DLC dimers, oligomers and polymers have attracted increasing attention [17][18][19][20][21][22][23][24] . The dynamics of discogens, such as rotation around the column axes, fluctuation in the column, and slippage out of column, has been partially inhibited by connecting two triphenylene mesogens via a spacer. Thus, the dimers show more ordered and stable Col mesophase and im-
