Study On The Design,Synthesis And Properties Of Liquid Crystal Molecules Based On Expanded Tetrathiafulvalene (TTF)

Liquid crystal is a very important soft substance with the fluidity of liquid and the anisotropy of crystal.At present,designing and synthesizing novel liquid crystal molecules and exploring the relationship between the structure and performance of liquid crystal molecules are still at the forefront of research in the field of liquid crystals.We chose expanded tetrathiafulvalene with unique topological structure and electrochemical properties as the mesogenic unit to design and successfully synthesize a series of liquid crystal compounds with novel molecular structure.The main research contents are:1.Two series of liquid crystal molecules with pyridazinanthraquinone extended tetrathiofulvalene structure were synthesized.The oxidation of ex-TTF leads to loss of aromaticity,thereby stabilizing the free radical cationic species of the resulting product.The electron-withdrawing ability of the pyridazine unit can reduce the HOMO energy level of the molecule and can increase the rigid structure of the molecule.By differential scanning calorimetry(DSC),it was found that compounds 12a(n = 12)and 12b(n = 16)have liquid crystallinity,while the liquid crystallinity of the target compound 12c(n = 18)with longer terminal alkyl chain will disappear And,the incompatibility of the flexibility of the molecules will also lead to compound 18a(n = 16)and compound 18b(n = 18)not possessing liquid crystal properties.The polarized light microscope(POM)with a hot stage can preliminarily confirm that the liquid crystal phases of the compounds 12 a and 12 b having liquid crystallinity are smectic phases.Liquid crystal forming compounds 12 a and 12 b obtained by small-angle X-ray scattering(SAXS)are arranged in a hexagonal columnar shape with 2 molecules in cross-section at normal temperature or high temperature.According to theoretical calculations,the target compound 18 is a typical D-?-A molecule.2.Synthesized a series of anthraquinone with cholesterol unit to expand dithiofulvalene liquid crystal compound.Cholesterol is recognized as a good mesogenic unit,and most cholesterol esters exhibit a liquid crystal phase.By introducing cholesterol units into the hard aromatic part,cholesteric liquid crystals can be easily prepared.Through differential scanning calorimetry(DSC),compounds 21a(n = 6),21b(n = 7)and 21c(n = 8)all have liquid crystallinity,and with the increase of the alkyl chain spacer,The glass transition temperature and clearing point temperature decrease.The polarized light microscope(POM)with a hot stage can initially determine that the liquid crystal phases of compounds 21 a,21b,and 21 c with liquid crystallinity are smectic phases.Liquid crystal forming compounds 21 a,21b,and 21 c obtained by small-angle X-ray scattering(SAXS)are arranged in layers at room temperature or high temperature.