Synthesis And Mesomorphism Of Triphenylene Discotic Liquid Crystal Dimers

Triphenylene liquid crystals can self-assemble into highly ordered columnar mesophase and possess high mobility of charges and energy, therefore, they show huge potential application as organic electronic materials. The most of much research on triphenylene liquid crystals have been to modify monomers'molecular structure in order to increase the columnar order. This thesis reported triphenylene discotic liquid crystal dimers in order to know the structure-property relationship of these dimers. Liquid crystal dimers which contain two mesogenic groups linked via a spacer can serve as ideal model compounds in liquid crystal polymer investigation, Thus, further exploration of the synthesis, characterization and structure-property relationships of triphenylene liquid crystal dimers is necessary.The thesis consists of five chapters:1. Chapter one briefly introduced the elementary knowledge about liquid crystal materials, including the definition and classification of liquid crystals; Then mostly introduced the studies on triphenylene liquid crystal dimers; At last briefly introduced Glaser coupling reaction.2. In chapter two, we reported the synthesis of eleven soft chain-bridged triphenylene discotic liquid crystal dimers by the esterification or etherification reaction. The results showed that, these triphenylene dimers showed columnar mesophase; compared with ethers bridged triphenylene dimers, esters bridged triphenylene dimers had wider mesophase ranges; dimer which had higher molecular symmetry showed higher clearing points. 3. In chapter three, we reported the synthesis of eight diacetylene-bridged triphenylene discotic liquid crystal dimers which had longer spacer by Eglinton coupling reaction. The results showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers; most of dimers had glass columnar phase, and no crystallization was observed above -50 oC for all the triphenylene dimers; dimer which had higher molecular symmetry showed wider mesophase range.4. In chapter four, we reported the synthesis of five diacetylene-bridged triphenylene discotic liquid crystal dimers which had shorter and more rigid spacer by Eglinton coupling reaction. The results showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers, only when n were 6 and 8, did dimer show columnar mesophase; the connecting group, length and rigidity of spacer had important influence on the mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers.5. Chapter five gave the summary and conclusion of the thesis.