Design,Synthesis And Self-assembly Of Thiadiazole Azobenzene Polycatenar And Tetrathiophene Bolaamphiphile,Triazine Wedge Molecules

Liquid crystal(LC)is a mesophase state between the crystal and the liquid,which combines the periodicity of the crystal and the fluidity of the liquid.Liquid crystal has properties of self-healing,stimulating response and adaptability.LCs have become a new type of intelligent materials.The design and synthesis of heterocyclic organic functional materials are attracting greatly attention because the introduction of heterocycles affects the properties of the compounds,especially the self-assembly behavior of the liquid crystals and the photoelectric properties.Hence,the introduction of the heterocyclic ring into the liquid crystalline molecules is expected to form complex liquid crystalline phases and impart excellent photoelectric properties on the liquid crystals.The first chapter is about the design,synthesis,self-assembly,ion recognition and photoelectric properties of azo 1,3,4-thiadiazole polycatenar molecules.Firstly,we introduced the research progress of liquid crystalline molecules containing 1,3,4-thiadiazole units and azobenzene units,which are mainly composed of rod-shaped,wedge-shaped,banana-shaped,polycantenar,discotic molecules.Then we described briefly the reviewed compounds containing 1,3,4-thiadiazole units which had the abilities of ion recognition and organogel formation.Finally the polycantenar liquid crystals were introduced.we have designed polycantenar liquid crystals conating azobenzene and 1,3,4-thiadiazole units.The self-assembly,ion recognition and photoelectric properties of azo 1,3,4-thiadiazole polycatenar molecules were studied.With changing the number,length and position of the terminal alkyl chains,not only smectic C phase and hexagonal columnar phase,but also micellar cubic(CubI/Pm3n)phase could be found in these compounds.Fluorescence gel can be formed in ethanol.They had reversible photoresponsive properties in solution,liquid crystalline states and gel states.Such compounds had lower energy gap and could be used as potential organic semiconductors.They also showed fluorescent emission with large Stokes shift in solution and binding selectivity to Cu2+ among a series of cations and couldcontinuously identify iodide ions in CH3CN-CH2Cl2 solution.In the second chapter,we firstly reviewed the self-assembled gels of oligothiophene,then the design,synthesis,self-assembly and photoelectric properties of tetrathiophene bolaamphiphile molecules were reported.Our group has recently reported that a series of oligothiophene bolaamphiphiles self-assembled into triangle,tetragonal,pentagonal,hexagonal and other polygonal honeycomb-shaped liquid crystalline structures,but the self-assembly behavior of these oligothiophene bolaamphiphiles in organic solvents as well as the device performance of these oligothiophene bolaamphiphiles have not yet been studied in-depth.Therefore,in this chapter,tetrathiophene bolaamphiphile molecule 4T-4C14 was designed to study its self-assembly behaviors both in pure states and in solvents.The compound was synthesized by Kumada and Suzuki coupling reactions as key steps.Compound 4T-4C14 was not a liquid crystal,but could form gels in the DMF solvent under ultrasound irradiation.UV spectra,cyclic voltammetry and impedance spectroscopy investigations indicated that the energy gap of 4T-4C14 was about 2.23 eV,the conductivity was about 0.88×10-6 S m-1 therefore 4T-4C14 has potentials as a new type of organic semiconductor material.In the third chapter,firstly the study progress on the liquid crystalline compounds containing 1,3,5-triazine unit was briefly reviewed,then the design,synthesis and self-assembly of the triazine wedge shaped molecules were introduced.The reported triazine compounds had taken triazine as the central nucleus to form three axi-symmetric structures beneficial to molecular self-assembly.Such compounds with the electron deficiency could be applied as n-type semiconductors and nonlinear optical(NLO)materials,organic electroluminescent devices(OLEDs)ect.Our group has previousely studied the taper shaped triazine derivatives in which CubI/Im3m-CubI/Pm3n was found.In order to find new mesophase phase and improve the photoelectric properties of triazine based compounds,in this charpter,we designed new triazine derivatives 1T3/n in which extra benzol ring was introduced in the rigid core,it was found that Colhex and micelle cubic phase(CubI/Pm3n phase sequence was appeared with the increase of the length of the terminal alkyl chain,But no Cubi/Im3m phase had been observed in these compounds.Therwfore extension of the rigid cores was not conducive to the formation of cubic phase.Compound 1T3/18 and barbituric acid derivatives could form hydrogen bond complexes and caused fluorescence quenching of 1T3/18.This method of formation of hydrogen bond complexes is expected to adjust the liquid crystalline properties and photoelectric properties of the composite system.The fourth chapter is the experimental part of azo 1,3,4-thiadiazole polycatenar molecules,tetrathiophene bolaamphiphile molecule,wedge shaped triazine molecules and the synthesis methods and spectral datas.