Synthesis,Self-assembly And Characterization Of Three Kinds Of ?-cyanostilbene-based Triblock,Star Shaped Tetraphenylethylen-based And Benzothiadiazole-based Bolaamphiphilic Liquid Crystal Materials

Liquid crystal(LC)combines order of crystaland fluidity of liquid in the molecular level,therefore liquid crystal system exhibits stimulation responsiveness,adaptability and self-healing properties.LC chemistry has become an excellent representive in the research area of self-assembly.By introducing the?-conjugated functional units such as AIEE(aggregation induced enhanced emission)groups including?-cyanostyrene(CS)and tetraphenylethylene(TPF)and heterocyclic fluorophores such as thiadiazole,oxadiazole and benzothiadiazole into the rigid parts of the LC molecules,complex self-assembly structures with novel functions could be obtained.It would be valuable to study functional LCs.In order to obtain functional liquid crystalline materials with aggregation-induced luminescence effects,organogel properties and multiple responsiveness,?-cyanostyrene and tetraphenylethylene units were introduced into rod-like and disk-like liquid crystal molecules respectively.In view of the strong assembly ability of the bola amphiphilic molecule,and the excellent photoelectric properties of oligothiophene and benzothiadiazole,oligothiophene-containing benzothiadiazole units were introduced into bolaamphilic liquid crystalline molecules.The research target is to achieve excellent self-assembly and electro-optical properties and find the releationship between the molecular structures and LC phases.Thus in this thesis,three seriesof liquid crystalline molecular systems were designed and synthesized,including?-cyanostilbene-based triblock LC compounds,star-shapedtetraphenylethylen-based LC compounds and benzothiadiazole-based bolaamphiphilic compounds.The self-assembly and photophysical properties of these three series compounds are systematic studied.LC and gelation self-assembly structures are obtained,the optoelectronic properties and devices of related systems are studied in an initial statge.Chemosensors and white light emission devices are obtained.The first chapter is the literature review including the following aspects:the first is the research progress of triblock liquid crystalline compounds,the second is the research progress of?-cyanostyrene based and tetraphenylethylene based liquid crystals and gels,the third is the research progress of bolaamphiphiles,the fourth is the research progress of benzothiazole based liquid crystal.In Chapter 2,the synthesis,self-assembly,aggregation-induced emission and chemosensor properties of triblock LC compounds containing?-cyanostyrene were investigated.These triblock compounds CN¹/n(n=6,12)with one terminal alkyl chain can self-assemble into bilayer Sm C or Sm A liquid crystalline phase.While the triblock compounds CN³/n(n=12,14,16,18)with three terminal alkyl chains can self-assemble into Col_hex/p6mm LC phase.These compounds can self-assemble into organogels with different morphologies in different organic solvents.They exhibit aggregation-induced luminescence and mechanoluminescence.After complexed with Li⁺ion,the complex showed more stable LC phases and conductivity.These triblock compounds CN³/n show specific recognition ability for Fe³⁺and the FT-IR spectroscopy showed that the recognition sites might be oxygen atoms in the polyether chain.The results show that these triblock compounds have potentials in the fields of aggregation-induced emission materials,reversible pressure sensitive materials and fluorescent sensors.In Chapter 3,the synthesis,self-assembly and aggregation-induced emission properties of star-shaped tetraphenylethylene based LC compounds were investigated.These star-shaped LC compounds TPE/n(n=8,12)with short peripheral alkyl chains can self-assemble into Col_hex/p6mm phase,where as the high analogues TPE/n(n=14,16,18)can self-assemble into columnar phase Col_hex/p6mm at lower temperature and the rarely occured three dimensional cubic phase Cub_I/I m3m at higher temperature.TPE/12 can form organogels with sphericalmorphology in ethyl acetate and porousmorphology in 1,4-dioxane.These star-shaped TPE compounds also exhibit aggregation-induced luminescence properties.When such TPE mesogens are dispersed in nematic LC 5CB,dichroic ratio values up to 6.34 are obtained.Furthermore the emission colors of both pure TPE mesogens and the doped gel formed by doping TPE mesogen with DPP dye are tunable.Remarkably white light emission(WLE)organogel obtained by doping such TPE mesogen with DPP dye can be further applied to fabricate white organic light emitting metreial by dispersion the WLE gel into poly(ethylene glycol)(PEG)film.The results show that these star-shaped TPE mesogens have potential applications in the fields of aggregation-induced emission materials and white light-emitting materials.In Chapter 4,the synthesis and self-assembly of two series of benzothiadiazole-basedbolaamphiphileswereinvestigated.For benzothiadiazole-bolaamphiphiles compounds containing two thiophenes,the compound BT²/n can self-assemble into a square honeycomb column phase with a two molecular wall thickness,for benzothiadiazole-bolaamphiphiles containing four thiophenes compounds,as the length of the pendant alkyl chain increases,these compounds exhibit a phase sequence of Col_hex?/p6mm-Col_squ/p4mm transition.The short-chain compound BT⁴/8 can self-assemble into a triangular honeycomb column phase of a two molecular wall thickness,while the long-chain compound BT⁴/n(n=12,16)can self-assemble into a square honeycomb column phase of a two molecular wall.The gelation ability of BT²/16 in different organic solvents were investigated.The SEM images of the xerogel formed in acetone showed nanorod structure and the SEM image of the xerogel formed by BT²/16 in n-butanol revealed a 3D network structure composed of partially left-handed helical entangled fibres.The solvent discoloration effect of the compound was investigated.The emission peak of BT²/16showed a significant red shift from 632 nm to 687 nm with different solvent polarities.The emission peak of BT⁴/16 showed a large red shift from 688 nm to 735 nm.The results show that the photophysical properties of the two series of compounds are strongly dependent on the polarity of the solvent,which may be due to the electron-donating thiophene unit and the electron-accepting benzothiazole unit.There is a distortion of the intramolecular charge transfer(TICT)effect.Compound BT²/16was mixed with a compound emitting blue fluorescence and yellow-green fluorescence to obtain a mixed solution having white light emission.In Chapter 5,the conclusion,innovation,deficiency and prospect of the thesisare provided.In Chapter 6,the synthetic procedures of the six series of target compounds and the related spectral data are provided.