Design,Synthesis And Properties Of Conjugated Polymers Containing Tetraarylethylene Units

Conjugated polymers are an important part of organic optoelectronic materials and have drawn considerable attention to scientists due to their unique molecular structure,macroscopic processing performance and fascinating photophysical and photoelectric properties,which make them promising for applications in organic light-emitting diodes,fluorescence sensors,biomedical imaging and other fields.Conventional conjugated polymers are prone to form ?-? stacking in the aggregated state,which cause the fluorescence intensity sharp weakened or even completely lost,showing aggregation caused quenching(ACQ).In contrast,conjugated polymers containing aggregation-induced emission(AIE)-characteristic units can avoid the fluorescence quenching of the polymer in the aggregated state.Base on this strategy,numerous AIE-active conjugated polymers have been designed and synthesized,and among them the conjugated polymers containing tetraarylethylenes(TAEs)are of greatest concern.In this dissertation,we described a new methodology of synthesizing conjugated polymers containing tetraaryl ethylene structural units by the means of geminal cross-coupling(GCC)of 1,1-dibromoolefins.The details of the dissertation are summarized as follows:1.In first chapter,we briefly introduce the phenomenon and mechanism of aggregation induced emission,tetraarylethylene(TAE)analogues,and the classifications,synthesis and applications of conjugated polymers containing tetraarylethylene(TAE)units.Finally,the design conception of this dissertation is described.2.The approach of geminal Suzuki cross-coupling of 1,1-dibromoolefins for synthesizing linear conjugated polymers containing tetraarylethylene units has been proposed.The optimum polymerization conditions were obtained through investigating the model polymerization.On the basis of this,a series of linear conjugated polymers containing tetraarylethylene units were obtained by polymerization of different aryl 1,1-dibromoolefins and aryl borates.It has been found that these polymers show good thermostability,tunable emission spectrum and typical AIE properties.In addition,according to the tendency of cyclization in the polymerization reaction,an AIE-active macrocyclic molecule containing three TPE units was synthesized and isolated,and the structure of the macrocyclic molecule was characterized by MALDI-TOF MS and 1H NMR.The approach of geminal Suzuki cross-coupling of 1,1-dibromoolefins for synthesizing linear conjugated polymers containing tetraarylethylene units can generate the tetraarylethylene unit in situ,which endow the polymers with typical aggregation-induced emission properties.This approach provides a simple and efficient strategy for designing and synthesizing novel AIE-active conjugated polymers,which is expected to highly enrich the variety of AIE materials.3.A series of neutral polymers POaFb + 1 and cationic polymer POaFb+1 + with varied ratio of fluorene units and tetraarylethylene units were designed and synthesized on the basis of geminal Suzuki cross-coupling of 1,1-dibromoolefins.The effects of fluorene units and tetraarylethylene units on the optical properties and AIE properties of the polymers have been investigated by introducing tetraarylethylene units to the traditional ACQ-characteristic polyfluorene.It has been found that the incorporation of tetraarylethylene units into traditional conjugated polymer can change their optical properties,which makes it possible to convert ACQ-characteristic polymers into AIE-characteristic polymers.It is further proved that tetraarylethylenes are very effective AIE-active groups.The water-soluble cationic conjugated polymers were obtained by quatemizing these neutral polymers containing the alkyl bromide side chains.The fluorescence responses of these cationic conjugated polymers to heparin were studied by the titration experiment of heparin.It has been found that the polymer PO0.7F1.3+,PO0.5F1.5+ and PO0.3F1.7+ show both fluorescence enhancement responses and fluorescence quenching responses to heparin,compared to PO1F1+ or PO0F2+.Wherein the polymer PO0.7F1.3+ exhibits the highest fluorescence response to heparin,with a detection limit of 9 nM,indicating that it can be used as a highly sensitive fluorescent probe to heparin.4.Monodisperse linear and hyperbranched conjugated polymer nanoparticles have been prepared by dispersion polymerization using geminal Suzuki cross-coupling of 1,1-dibromoolefins.The acquired nanoparticles are well-defined,and the associated particle sizes can be adjusted by altering the concentration of the initial monomers.Both types of polymers,constructed with multiple topological units of TAEs,show boosted fluorescence in aqueous dispersion in comparison with their soluble state in 99%THF solution,which exhibits the archetypal AIE behavior.Furthermore,we prefered to choosing the emissive suspension of P2 nanoparticles as a demonstration to detect the nitro-explosives,which achive a good sensitivity and superamplified quenching effect for PA.This investigation on the preparation of size-tunable monodisperse AIE-active conjugated polymer nanoparticles probably offers new opportunities to extend the application of AIE materials in self-assembled colloidal photonics and tracking cellular activities.5.Based on the approach of geminal Suzuki cross-coupling of 1,1-dibromoolefins,we have designed and synthesized a series of conjugated organic porous polymers containing TAEs units.These porous polymers possess good chemical stability and thermal stability,and emit the fluorescence in the near infrared region.Nitrogen adsorption analysis shows that the maximum Brunauer-Emmett-Teller(BET)surface area of these porous polymers is 728 m2/g and the dominant pore size is centered at 2.5 nm,indicating that this approach is suitable for the synthesis of porous polymers.In addition,dispersible conjugated cross-linked polymer nanoparticles were synthesized by miniemulsion polymerization using geminal Suzuki cross-coupling of 1,1-dibromoolefins.The obtained nanoparticles have spherical morphology with a diameter distribution of about 200 nm,which can be dispersed in common organic solvents and are promising for application in fluorescence sensors.