Discotic Liquid Crystalline Triphenylene Derivatives As Optoelectronic Materials: Synthesis And Characterization

This thesis is focused on the investigation of the synthesis of triphenylene-based discotic liquid crystals, and the mesogenic properties of the materials. There are three main sections in the dissertation.The first section includes the synthesis of monohydroxypentaalkoxytriphenylene and dihydroxytetrahexyloxytriphenylene. Using novel synthesis methods of tripheny-lene, the aims were realized, improving the reaction yields, cutting down the cost of production and providing the starting materials conveniently for further investigation. In addition, the acrylate derivatives and methacrylate derivatives of dihydroxytetrahexy-loxytriphenylene were also synthesized. Furthermore the mesogenic properties of the isomers of the acrylate derivatives and methacrylate derivatives were studied. These experiments and conclusions were included in chapter three and chapter four, respectively.The second section includes the synthesis of perylene bisimide-bridged triphenylene dimers and tetraalkoxytriphenylene-1,4-dione. The four triphenylene dimers were found to having light absorption in the visible range, and having fluorescence in dichloromethane solution (λmax= 533 nm). When the spacers between the core of perylene bisimide and that of triphenylene are decyloxy, the dimer (PBI10TP6) is mesogenic. When the mixture of PBI10TP6 and P3HT acted as the active layer, the photovoltaic device had improved properties. The tetraalkoxytriphenylene-1,4-dione has absorption in the range of 250-630 nm, and can form stable mesophase upon heating and cooling circles, when the pentyloxy and heptyloxy are used as side chains, respectively. Chapter five and chapter six are composed of these experiments.The third section is about trying to synthesis of hexaalkoxyhexa-peri-hexa-benzocoronene (HBC) not using the derivatives of diphenylacetylene. The purpose was to reduce the cost of starting materials, and to obtain novel hexaalkoxyl substituted HBC. The synthetic scheme was preparing pyrylium salts firstly, then synthesizing tetraphenylbenzene, and then obtaining the precursor of HBC, which was oxidized to obtain the target product. Unfortunately, the last step of the reaction was not succeeded, for 12 hydrogen atoms had to be removed in the reaction. For more details, please look at chapter seven.