Synthesis And Characterization Of Conjugated Oligomers And Polymers Containing Pyrene Units

Pyrene is not only a very good blue chromophore, but also an excellent electron acceptor.Pyrene and its derivatives has a unique fluorescence as a typical polycyclic aromatichydrocarbons. In recent years, conjugated organic molecules because of their special opticaland electrical properties has caused widespread concern growing, based on conjugatedpolymers broad application prospects and business value, people on the one hand continue toimprove and develop the traditional classical method, on the other hand to explore the newsynthesis process to improve the structure of conjugated polymers and performance, wideningits field of application. Conjugated ladder polymer is an important branch of conjugatedpolymer, which can be applied to the field effect transistors, electroluminescent devices,photovoltaic devices, thin film laser and other fields.The main contents of this paper are as follows:1. Synthesizing three groups oligomers conjugated that containing pyrene units, and theyall exhibit bright blue fluorescence in dichloromethane solution. Determining the fluorescencequantum yield in solution of toluene, the maximum yield of them is7c, which is49%, and thedata shows that the trans-structure compounds has a higher fluorescence quantum yield thanthe cis-structure compounds.2. The pyrene was used as a starting material, and a new monomer M1(pyrene-2,7-bis(4,4,5,5-tetramethyl-[1,3,2]dioxaborolane) was synthesized. Then M1has polymerizedwith the other monomer which has methoxy functional group, which can conduct directlyintramolecular ring-closure after polymerization to get the ladder structure, avoiding reductionor addition reaction in the polymers.3. The p-bromophenol was used as a starting material, the monomer M3and M4weresynthesized, which can be used to synthesis the ladder polymer LP2and LP3by the Suzukicoupling reaction with (pyrene-2,7-bis(4,4,5,5-tetramethyl-[1,3,2]dioxaborolane). Theresulting polymers were characterized by GPC, which have large molecular weight, the Mnand Mw of polymer LP1were12500and54200; the Mn and Mw of polymer LP3were11600and45600. The polymer were characterized by UV-vis absorption and photoluminescencespectra, the absorption and emission peaks of the ladder polymers LP1and LP3shiftedtoward low energy. The polymers P1and P3exhibited a absorption band in the ultraviolet region with a maximum at357and330nm, after ring closure the ladder polymers LP1andLP3show a very broad band in the the UV-vis absorption spectra with not clearly peaks, theabsorption band of polymer LP1was between300and450nm, the maximum absorptionband and the maximum emission bands of LP3are peaked at350and508nm, respectively.TGA thermograms of the two polymers exhibit good thermal stability. Weight loss (5%) startsat339°C and249°C for LP1and LP3, and until when LP3was heated up to800°C,22%weight of polymer is not completely decomposed. DSC analysis of the polymers showsneither a glass transition process (Tg) nor other thermal processes from50°C to300°C,which also can prove that it has a relatively high thermal stability. The target products aremeaningful for synthesizing blue fluorescent materials with thermal stability and highfluorescence yields.