Synthesis And Characterization Of Pyrene-based Planar Conjugated Oligomers And Polymers

Conjugated polymers not only have the characteristics of inorganic semiconductors,but also have the processability and flexibility of the polymer.Their skeletal structures and optoelectronic properties can be changed by adjusting the side chain structure of the polymer.Conjugated polymers have received tremendous scientific and industrial attention for their application in photovoltaic cells,image sensingand field-effect transistor.Pyrene is not only a very good blue chromophore,but also an excellent electron acceptor.Pyrene and its derivatives have a unique fluorescence as typical polycyclic aromatic hydrocarbons.This paper presents three 2,7-position planar conjugated polymer with three corresponding model oligomers.A kind of ladder-type conjugated polymer and two kinds of oligomers were synthesized in this study.The main contents of this thesis are as follows:1.Conjugated oligomers precursor which obtain benzene units,pyrene units and benzodioxan thiophene units were synthesized by Suzuki coupling reaction.By optimizing the cyclization reaction,we underwent oxidative cyclodehydrogenation with DDQ to give the planar conjugated oligomers W1,W2 and W3.The oligomers were characterized by UV-vis absorption and photoluminescence spectra,the absorption and emission peaks of the oligomers shifted toward low energy.The oligomers exhibited absorption bands in the ultraviolet region with maximum at 435,548 and 382 nm,respectively;the fluorescence maximum emission peaks were 476,568 and 474 nm,respectively.2.Using the above synthetic route,synthesized conjugated planar polymers LP1,LP2and LP3.Polymers are soluble in common organic solvents,for example,dichloromethane,tetrahydrofuran and so on.The UV-vis absorption and PL spectra of the planar conjugated polymers in dilute solution of dichloromethane showed slightly red-shifted with the increasing linear length.The thermal properties of the polymers were investigated by thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC)in a nitrogen atmosphere.LP1 and LP2 exhibited good thermal stabilities with onset degradation temperature at about 300^oC,and DSC analysis of the polymers shows neither a glass transition process(T_g)nor other thermal processes from 50°C to 300°C,but LP3 presented poor thermal stability.3.A ladder-type conjugated polymer and two kinds of model compounds containing pyrene units are synthesized.The precursorpolymer and model compounds are obtained through the Pd(0)-catalyzed Suzuki reaction,then the planar structure is formed through intramolecular cyclization in the presence of CF₃COOH.We investigated their UV-vis absorption and PL spectra properties,suggesting that red-shifted with the increasing linear length are happened in the polymer and oligomers.The thermal properties of the Polymers and model compounds were investigated by using thermogra-vimetricanalysis(TGA)and DSC.Polymer and oligomers own high onset degradeation temperature,which exhibited good thermalstabilities.All polymer and oligomers did not show any distinct T_g and T_m between50?300^oC in the DSC traces of second heating,these results also showed that they have good thermal stabilities.