The Functional Materials Based On Cyanostilbene Derivates: Stimuli Responsive Gels And Polymorphs

Due to the defects of aggregation caused quenching,the application of conventional ?-conjugated organic luminescent materials are largely limited in aggregated state or solid state.The discovery of molecules with aggregation induced emission has solved this problem fundamentally and has outstanding application value in many fields such as smart response materials,optoelectronic devices,biological applications and chemical sensing.As a member of AIE-gens,the cyanostilbene derivates are easy to be modified,after modifying with different functional groups,it can form fluorescent materials such as gels and crystals further.The former can be applied to the field of intelligent response materials,and the latter can be used to prepare optoelectronic devices and exerts its superior application value.With the progress of research on luminescent crystals,people began to focus on adjusting the luminescent properties of solid luminescent materials by various means.In recent years,the method of preparing polycrystalline phases by changing the molecular conformation and molecular packing has been widely concerned.In this thesis,the cyanostilbene derivates were used as the research object and they were modified with different functional groups,then the self-assembly properties and functional applications were studied in the gel state.In the crystal state,the fluorescence regulations of crystals were studied by designing polycrystalline phases.First,after introducing the N,N-dimethylaniline group to the V-type cyanostilbene skeleton,we designed and synthesized BAPBIA with a D-?-A structure,and its self-assembly properties and stimuli response abilities were investigated.Experiments indicated that BAPBIA possess the properties of aggregation induced emission enhancement and intermolecular charge transfer and it could form a yellow emission gel in different solvents such as acetonitrile.The BAPBIA gel showed multi-stimuli responses to heat,ultraviolet light,fluoride ion and trifluoroacetic acid,accompanied by reversible gel-to-sol conversion and fluorescence regulation.Among them,under the first three external stimuli,the gel collapsed and its fluorescence declined,while the fluorescence changes were quite different when the gel responsed to TFA.After the addition of TFA,the N,N-dimethylaniline groups undergo protonation and become electron withdrawing groups,the intermolecular charge transfer of the molecule iss destroyed.And the gel collapsed to solution with strong blue emission.After the addition of triethylamine,the gel formed again.Second,based on the structure of BAPBIA,in order to enhance the conjugate strength of the molecule,we deleted the amide bond groups and modified with the phenolic hydroxyl group and the trifluoromethyl functional groups to introduce the intermolecular hydrogen bonding,prepared two cyanostilbene derivatives with photoirradiation effect,the linear molecule,THBA and the V-type molecule,BTHTA.THBA could be prepared to two crystals with completely different morphology when the solvent volatilization speed was different: blue fluorescent needle-like crystal(THBA-B)and yellow fluorescent plate-like crystal(THBA-Y).The crystal structure and XRD spectrum showed that the two crystals were both lamellar packing with different long periods,while the molecular conformations of them were obviously different.The molecular conformation in THBA-B is very distorted,while in THBAY,the molecular conformation is close to the plane.Hence,the difference in crystal fluorescence is mainly due to the molecular conformation.BTHTA could prepare two kinds of bulk-like crystals with different emissions in different solvents: a blue emission crystal containing chloroform solvent molecules,BTHTA-B and solventfree yellow emission crystal,BTHTA-Y.The data show that the molecular packings of the two crystals are completely different,and the packing way of molecules in BTHTA-Y is lamellar paking.Meanwhile,BTHTA-B contains one molecular conformation,while BTHTA-Y contains two molecular conformations,the two crystals have different molecular conformations.Therefore,the red-shift in fluorescence between the two crystals may be caused by the synergistic effect of different molecular configurations and different molecular packings.In addition,the BTHTA could form stable gels in a variety of solvents,and its xerogel film had a response to triethylamine atmosphere.This part of the work provides new insights for the design of polycrystalline systems and gels with high conjugate strength.