| Liquid crystal is the mesophase between liquid and crystal, which combines the mobility of liquid with the order of crystal. This special property makes LC become widely used in photo-electric material, organic solar cell, mechanical response and solvent response materials.Polycatenar liquid crystal refers to liquid crystalline molecule whose both sides of the rigid rod aromatic core connect symmetrically with a single or multiple flexible chains. The incompatibility between rigid rod aromatic core and flexible alkyloxyl chains leads to the formation of liquid crystal.These molecules can generate various mesophases including 2D smectic phase, columnar phase and 3D cubic phase. Research on this kind of molecule is important for the study of photo-electric liquid crystalline materials. It has become a hotspot to construct liquid crystals through hydrogen bonding interactions in recent years. Triazine unit contains both nitrogen atoms and amo groups which makes it good candidates for hydrogen bond formation. It also makes triazine as the basic unit for liquid crystalline compounds favored by many researchers.In this contribution, starting from commercial materials, through esterification, etherification, reduction and substitution, using Suzuki coupling, Sonogashira coupling and click coupling reaction as key steps, series of liquid crystal compounds were synthesized. They are liquid crystals based on 2,7-diphenyl-fluorenone and liquid crystal molecules based on 4,6-diamino-triazine. By adjusting the composition of center aromatic core, such as introduction of thiophene and acetylene to enlarge the conjugation of rigid core, and regulating the number or length of alkyl-oxyl chains we can modulate the type of liquid crystals. Interactions between inter-or intra-molecules drive liquid crystals to self-assembled into different kinds of 2D,3D structures, including Smectic phases, columnar phases (Col/p6mm, Col/c2mm, CoVp4mm) and cubic phases (Cub/Pm3n, Cub/Im3m). Study these phases in-depth conduce to further understand of self-assembly rules and design of high performance liquid crystalline materials.On the basis of the design and synthesis, structures of compounds were confirmed by 1-NMR,13C-NMR. Mesogenic behaviours are investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray scattering (XRD). Besides, UV-Vis spectra, fluorescence spectrum and cyclic voltammogram curves have been used to investigate their electricity properties. By density functional theory (DFT) Gaussian 09, the energy gap of different series was calculated and on this basis photoelectric properties are explained. |
