Synthesis And Study On Self-Assembly Properties Of Rod-Coil Liquid Crystalline Oligomer

In this thesis, three series of rod-coil liquid crystalline oligomers are synthesized, which are the n-type with anthracene in the rod block, the linear-type with biphenyl in the rod block and the v-type with pyrene in the rod block. And their self-assembly behaviors are studied at solid, liquid crystalline state as well as in solution. The effect on self-assembled structures by the minor changes in the structures of these molecules is discussed by changing such factors as the shape, the volume and the cross-sectional area of the flexible chains and the shape of the rod so as to find out the inherent laws between the molecular structure or shape and self-assembled aggregate structure.Four categories of n-shaped molecules consisting of n-typed rod blcok, alkyl chains and polyethylene oxide (PEO) chains are synthesized in the study of the n-typed rod-coil liquid crystal oligomers with anthracene in the rod block. We summarize the influence on the self-assembly structures of the n-shaped rod-coil liquid crystal oligomers by changing the length of hydrophobic alkyl chains in the center of the rod; changing the length of the alkoxyl chains at the end of the rod; changing the cross sectional areas of the alkoxyl chains at the end of the rod and the flexible alkyl chain. The research indicates that the self-assembly structures of these molecules transform from hexagonal column to rectangle column in liquid crystalline phase and form diameters increasing nanofiber structures in aqueous solution with the increase of the length of hydrophobic alkyl chains in the center of the rod. For molecules of alkoxyl chains at the end of the rod, with the increasing of the length of alkoxyl chains, an oblique columnar structure comes into being and then transfers into isotropic liquid. While changing the cross sectional areas of alkoxyl chains, with the increasing of the cross sectional areas, the molecules cannot form self-assembly at room temperature but forming rod-like micelle in aqueous solution. The n-shaped molecules containing octadecyl flexible chains self-assemble into layer structures in solid state, and have no liquid crystalline phase.Two categories of linear-typed molecules with several biphenyls as rod and with polyethylene oxide (PEO) or polypropylene oxide(PPO) as flexible chains are synthesized in the study of the linear-typed rod-coil liquid crystal oligomers with terphenyl in the rod block. we discuss the influence of the length of lateral chain in the center of the rod on molecular self-assembly structure as well as the self-assembly property of the molecule with an active group in the center of the rod. The results indicates that the introduction of longer lateral chain in the center of the rod building blocks will destroy the interaction ofπ-πstacking, thus makes the self-assembly structure of the molecules transform into disordered arrangement. The molecule with vinyl group in the center of the rod is performed by photo-polymerization in liquid crystalline phase. The resulting polymer can retain the nano-structure of the liquid crystalline phase, even though the temperature descends to room temperature.A series of molecules based on pyrene unit in the center of the rod, with the same volume fraction of the flexible chains and different cross sectional areas are synthesized in the study of the v-typed rod-coil liquid crystal oligomers. The influences on molecular self-assembly by the shapes of the rod (v-type and linear type) and the cross sectional areas of the flexible chains are discussed. The results imply that the dendritic chain with larger cross sectional area evidently destroys the self-assembly of rod building block. The molecules with line type rod prefer to form nematic phase in liquid crystalline phase, while the v-shaped molecules cannot form liquid crystalline phase.