| Liquid crystals (LCs) combine order and mobility at a molecular level so that systems can take the lowest energy conformation in response to external (magnetic, electric field, chemical and mechanical) stimuli. Liquid crystals can exhibit excellent properties in many ways. Ionic liquid crystals which integrate the properties of liquid crystals and ionic liquids are a class of liquid- crystalline compouds that contain anions and cations. Typical properties for ionic liquid crystals are the ion conductivity, and therefore they have been widely used as ionic conductive materials, organic reaction media and functional nano-materials. Combining the self-organization forces of liquid crystals with the unique solvent properties and ion-conducting properties of imidazolium ionic liquids yields imidazolium based ionic liquid crystals (ILCs). These LC materials lead to novel applications such as in direction dependent ion-conducting materials and have improved the light-to-electric energy conversion efficiency of dye sensitized solar cells. Hence for exploration the further applications, the study of the self-assembly behavior and the structure-property relations of imidazolium based ILCs is essential.In this thesis, a series of rod-like phenylimidazol benzoates containing terminal alkoxy chains were synthesized via copper (I) catalyzed Ullmann coupling reaction as key step. Their mesogenic behaviors were investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray scattering. The effects of length and number of alkyl chains on the LC properties of phenylbenzoate based rod-like imidazolium salts were systematic studied. By changing the length and the number of the terminal alkoxy chains at the benzoate moiety and alkyl chain attached to the imidazole moiety, nematic(N), smectic A(SmA), hexagonal columnar(Colhex) and micellar cubic phases (CubI) can be found in these compounds. As far as we know, this is the first time that micellar cubic phases are found in such imidazolium based ILC with extended rod-like aromatic cores. The initial relationship between the molecular structures and their mesophorbic characters was found. The reason of forming these mosophases was analyzed from the aspect of self-organization. Our study should provide some important information for the application of these compounds. At the same time, antitumor activities and structure relationships of these imidazolium compouds were also studied. Several compounds displayed potent cytotoxic activity. Finally, a series of wedge-shaped multi-ethers compounds containing terminal alkoxy chains were synthesized in order to study the relationship between the molecular structures and their mesophorbic characters. By changing the length of the terminal alkoxy chains, SmA phase can be found in these compounds. |
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