Discotic liquid crystal (LC) molecules have a structure that is comprised of a rigid aromatic core with side-chain molecules. Intermolecular £k-£k interactions force the tube to orient and form one-dimensional columnar structures which can act as molecular wires. In recent years, discotic LC molecules have been deposited on surfaces from solution to create the solid-state electronic elements used widely in solar cells, organic light-emitting diodes (OLED), organic photovoltaic, field-effect transistors (FET), and molecular wires. Different stacking morphologies can change the behavior of the material and thus will have potential for different applications. Hence, effective control over the stacking of the LC molecules on surfaces is important for optimizing the performance and effectiveness of LC-based electronic components and devices. This study has focused on LC molecules with acid and ester containing functional groups, and how these groups influence the stacking behavior on surfaces. Here, the self-aggregation behavior of the discotic LC ester in solution was investigated quantitatively by determining the concentration dependence of the 1H NMR chemical shifts. Our results showed that discotic LC ester has different self-aggregation behavior in CH2Cl2, THF and Benzene organic solvents. THF solvent showed the highest degree of aggregation, followed by CH2Cl2, and then benzene. We also studied the effects of (i) different solvents (THF, CH2Cl2, and Benzene), (ii) different surface functional groups (OH, CH3, NH2, SH, and diphenyl), and (iii) temperature, on the stacking phenomenon of discotic LCs on silicon surfaces. In part (i) our results showed that discotic LC ester had different morphologies on silicon surfaces due to differences in solvent polarity and evaporation rate. In part (ii), we observed that different surface functional groups did not affect the intermolecular interaction between either the ester- or acid-type LC molecules. For the acid-type LC, strong hydrogen bonding interactions with the surface caused the crystals to form rod-like fiber structures. However, the ester-type LC molecules formed ribbon-like stacks on the surfaces. For functional groups containing CH3 (more hydrophobic surfaces), we observed no LC molecules on the surface, which was likely due to the poor wettability of the solvents on OTS. In part (iii), we observed that both acid and ester discotic LCs formed large aggregates on the surfaces due to a ¡§ripening effect¡¨. With increased temperature, the molecules were able to overcome the wetting interaction with the surface and self-aggregate into three-dimensional clusters.

Disc like molecule which was formed by fused polyaromatics was found to be with discotic liquid crystal properties. So it has been researched thoroughly. We take 5,6,11,12,17,18-hexaazatrinaphthylene (HTN) as our central core and synthesize Hexa-O-substituted hexaazatriphenylene, a new molecule with discotic liquid crystal properties successfully.

Because of the unique physical properties of liquid crystal molecules, such as: light, electricity, magnetic anisotropy, they exhibit different values, the most known current application on displays in our life. As the liquid crystal molecules can be modified through the functional groups, thereby affecting its physical properties, it caused great interests in synthetic chemists. In this thesis, we synthesized liquid crystal based on dibezo[a,c]phenazine core and the dioxole skeleton was also induced into dove-tail alkyl chain functional group surrounding the central aromatic core . Moreover, we also change the chain length of alkyl chain to explore stacking arrangement structure of the mesophase. By the various instruments to explore the nature of stacking, we preliminary assumed that the mesophase might exhibit the helical stacking with excellent charge mobility, which could be good candidates for optical and electrical applications.

Discotic liquid crystals (DLCs), which consist of disc-like molecules, are known to be able to form nematic and columnar mesophases through self-assembly. Because of the high electric charge mobility in one-dimension, DLCs are found to have uses in making electronic and photonic devices, such as organic light emitting diode, photovoltaic and molecular wires. In order to achieve better performance of these applications, it is essential to obtain the desired alignment of the DLCs. The purpose of this study is to investigate the stacking of disk-like molecules and to control their alignment. The materials used in the present studies are HDBP-8 and LC10. In this thesis, we will show that the stack of disk-like molecules is strongly influenced by temperature. We will also discuss how the molecules stacking is influenced by surface free energy. The disk-like molecules tend to stack with face-on when the surface free energy of the substrates is high. On a surface with lower surface free energy, molecules tend to stack with edge-up. In the latter part of the research, substrates are specially treated to have different surface free energies, and molecular stack on these substrates is observed.

In this thesis we synthesize discotic liquid crystal materials. After demonstrating the molecular structures by 1H-NMR of Acid-6, we measure the properties of this material. We use discotic liquid crystal Acid-6 and measure its¡¦ properties. It shows the properties of Acid-6 which is having the ability of absorbing visible light. By UV-Vis spectrum, we can realize the absorption band is located at 400 nm and confirm that it is able to be a photo-sensitized dye. Besides, the property of discotic liquid crystal is the self-assembly ability, the molecular can assemble into hexagonal columnar structure by themselves, which enable discotic liquid crystal to have better mobility. The DSSCs have good power conversion efficiency with using discotic liquid crystals Acid-6. We can measure its¡¦ mobility to know the component with which the most appropriate.

Discotic liquid crystals (DLCs), which consist of disk-like molecules, have recently attracted considerable attention for their interesting electronic properties. One of the most significant of DLCs is their high charge carrier mobility in their columnar structure. Recently the number of researches have been increasing on applications such as organic light-emitting diodes (OLED), photovoltaic devices (OPV) and organic field-effect transistors (OFET). The purpose of the study is to investigate the mobility of different alignment of DLCs. The material used in the present study is HDBP-8. We will show that the stack of DLCs depended on temperature strongly. We will also discuss charge transport properties of homeotropic alignment. Carrier transport has been investigated in the hexagonal columnar (Colh) mesophase of HDBP-8 using time-of-flight (TOF) technique. The carrier mobilities are up to the order of 10-3 cm2V-1s-1 for both positive and negative charges with weak dependence on the electric fields.

The common discotic mesogen molecules are known to have a flat structure, comprising a rigid core, e.g., polynuclear aromatic structure, and a ring of four to nine flexible aliphatic side chains. We take the electron deficient heterocyclic hexaazatriphenylene (HAT) as our central core and readily synthesized by the condensation of hexaketocyclohexane with the respective 1,2-bis-alkoxy-4,5-diaminobenzene. The new molecules with electron deficient discotic liquid crystal properties are successfully.

The scarcity of research about nitrogen containing heterocyclic discotic liquid crystal has made it an interesting subject for chemists. In this thesis, we will discuss the synthesis and properties of four kinds of new dimeric discotic liquid crystal in details. The first type of new dimeric discotic liquid crystals were synthesized based on a novel core structure, dibenzo[a,c]phenazine. All dimers linked by a hexyl-chain spacer exhibited columar phase. The range of mesomorphic temperature became wide as the chain length of spacer increased. Simultaneously, we also changed terminal chain length to investigate the influence on mesomorphic properties by attached terminal group. The second type of new dimeric discotic liquid crystals, which contained the dibenzoquinoxaline skeleton, didn¡¦t show the properties of mesomorphic phase due to the poverty of planality. The third type of molecules, which also have the dibenzoquinoxaline skeleton, were the banana-shaped discotic liquid crystals. We anticipated these dimeric molecules would demonstrate another special mesogenic phase. The last type of dimeric discotic liquid crystals were the extension of our previously research. These molecules, which comprised 5,6,11,12,17,18- hexaazatrinaphthylene skeleton, would be good candidates for using as a n-type material.

In our laboratory, we using simple synthetic methods to synthesize one series of amphiphilic discotic liquid crystal which has the dipole-dipole forces. We not only research the effect about the length of hydrophilic chain, but also explore the arrangement of this series through some cross-comparison.

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