The Experimental Study Of Electrosynthsis Of Several Conducting Polyfluorene Derivatives As Light-emitting Materials

Electrochemical polymerization had been proved to be one of the most useful approaches for conducting polymer synthesis. In recent years, high-quality conducting polymers prepared from fused ring aromatic compounds by electrochemical polymerization had attracted great attention. Polyfluorene and its derivatives have been considered promising candidates as blue-light-emitting materials. Because of their highly efficient photoluminescence and electroluminescence, thermal and oxidative stability, good solubility, and emission of polarized blue light, they are especially suitable for applications to polymer light emitting diodes. High-quality conducting polymers have been easily produced using boron trifluoride diethyl etherate (BFEE) as the solvent and supporting electrolyte, especially when fused-ring compounds were used as the monomers. This dissertation focused on the electrosynthesis of high-quality conducting and light-emitting polymers from 9,9-dichlorofluorene, 9-hydroxy-9-fluorenecarboxylic acid, 9-aminofluorene in pure boron trifluoride diethkl etherate (BFEE) and 9-hydroxyfluorene in CH2Cl2 + 5% BFEE and CHCl3 + 5% BFEE. And the electrolyte composed of 9-hydroxy-9-fluorenecarboxylic acid and BFEE was also investigated.1. Poly(9,9-dichlorofluorene) films was electrosynthesized successfully by direct anodic oxidation of 9,9-dichlorofluorene using BFEE. The oxidation potential onset of 9,9-dichlorofluorene in pure BFEE was 1.67 V, which was much lower than that determined in acetonitrile containing 0.1 mol/L Bu4NBF4 (2.19 V). FT-IR and 1H NMR spectral investigations indicated that electrochemical polymerization of 9,9-dichlorofluorene mainly occurred at C2,C7 positions. In the fluorescence spectra, the emission peaks of poly(9,9-dichlorofluorene) in DMSO appeared at 537 nm, implying the green-light-emitting property of poly(9,9-dichlorofluorene). The electrical conductivity of poly(9,9-dichlorofluorene) films was measured to be nearly 10-1 S/cm. The conducting and light emitting properties will be greatly helpful for the applications of PDCF films.2. High quality poly(9–hydroxyfluorene) films with an electrical conductivity of 10?2 S/cm were successfully electrosynthesized by direct anodic oxidation of its monomer 9–hydroxyfluorene in CH2Cl2 + 5% BFEE and CHCl3 + 5% BFEE (by volume). FT-IR spectra and theoretical calculations showed that the electropolymerization of 9–hydroxyfluorene occurred mainly at C2,C7 positions. The fluorescence spectra suggested that poly(9–hydroxyfluorene) films were good blue–light emitters.3. High quality poly(9-hydroxy-9-fluorenecarboxylic acid) films were electrochemically synthesized in pure BFEE by the direct anodic oxidation of 9-hydroxy-9-fluorenecarboxylic acid monomer. The complexion of–OH and–COOH group of the monomer with BFEE increased the ionic conductivity of the electrolytes significantly. As formed poly(9-hydroxy-9-fluorenecarboxylic acid) film showed good redox activity and good electrochemical stability even in monomer–free BFEE and in concentrated sulfuric acid. FT-IR spectra, quantum chemistry calculations and 1H NMR spectra confirmed that the polymer chains grew mainly via the coupling of the monomer at C2,C7 positions. Fluorescent spectral studies indicated that poly(9-hydroxy-9-fluorenecarboxylic acid) with an electrical conductivity of 10?2 S/cm was a good blue–light emitter with fluorescence quantum yields of 0.045.4. Water-soluble poly(9-aminofluorene) films with an electrical conductivity of 0.28 S/cm were successfully electrosynthesized in pure BFEE by the direct anodic oxidation of 9-aminofluorene. According to the FT-IR and quantum chemistry calculations, the poly(9-aminofluorene) chains grew mainly via the coupling of the monomer at the C2,C7 positions. The fluorescence spectra suggest that soluble poly(9-aminofluorene) is a good blue-light emitter with good fluorescence quantum yields of 0.44 (doped) in water. BF3 was coordinated with R-NH2, which may have contributed to the good water solubility of poly(9-aminofluorene) in the doped state. However, the quaternary ammonium compound was formed when dedoped polymer films were introduced into 0.5 mol/L HCl, which made the dedoped polymer films soluble. However, formation of the quaternary ammonium compound was stunted by BF3, resulting in the lower solubility of the doped films in 0.5 mol/L hydrochloric acid. In 0.5 mol/L hydrochloric acid the doped and dedoped poly(9-aminofluorene) films were blue-light-emitters with fluorescence quantum yields of 0.40 (RNH2:BF3) and 0.17 (R-NH3+Cl-), respectively.