Synthesis And Investigation Of Triphenylene-based Discotic Liquid Crystals

Two series of triphenylene derivatives were prepared: one with a plane symmetry triphenylene diesters and the other are triphenylene dimmers bridged by a perylene linking group. These were synthesized by Willimenson double-coupling reaction, oxygenation cyclization, substituent, reduction etc. Target compounds were characterized using ~1H-NMR, MS, HRMS, MALDI-TOF MS, elemental analysis etc.Thermal properties of the two series of triphenylene materials were investigated using differential scanning calorimetry and polarized optical microscopy. The triphenylene diesters showed liquid crystal phases. The length of alkyl group on the ester side chains had a direct influence on the transition temperatures of the phases. The longer the side chains, the lower the transition temperature from crystal to liquid crystal and the higher the clearing temperature. However, triphenylene dimmers bridged by a perylene linking group did not show liquid crystals phase. During the course of heating, the materials had a distinct crystal-crystal phase transition at first, and these were then melted into isotropic liquid at high temperature. It is expected that these materials may have charge carrier transport properties including both hole and electron.Molecular simulation was also carried out using Gaussian software. The structure of the triphenylene diesters were optimized and calculated. The results were compared with the absorption spectrum of the triphenylene dimmers. The range of absorption was great expended by the perylene diamine.