Novel Conducting Polymers From Fused-ring Aromatic Compounds Via Electrochemical Polymerization

The field of conjugated polymers continues to attract great interest of many scientists due to their potential applications in the development and the construction of new advanced materials. However, even to date, despite the large amount of work devoted to the fundamental research of conducting polymers, it is widely perceived that the design and synthesis of novel conducting polymers with unique properties suffice for applications, such as good fluorescence properties, stable electroactivity, and favorable thermal stability, are still very necessary and significant, and apparently also a considerable challenge. As a useful and widely applied technique, electrosynthesis of conducting polymers on the electrode surface has been a very active research area in electrochemistry because of the outstanding properties of these materials, which allow the polymer-modified electrode to be used as sensors, catalysts, electrochromic materials, batteries, microelectronic devices, and also as corrosion inhibitors to protect semiconductors and metals. In recent years, high-quality conducting polymers prepared from fused-ring aromatic compounds by electrochemical polymerization have been attracting great attention. This dissertation mainly focused on the electrosynthesis and characterization of high-quality fluorescent conducting polymers from fused-ring aromatic compounds.1. The electrochemical polymerization study of a set of monomers, dibenzothiophene (DBT), benzothiophene-S,S-dioxide (BTO), and dibenzothiophene-S,S-dioxide (DBTO) was reported for the first time and novel conducting poly(dibenzothiophene-S,S-dioxide) (PDBTO) was successfully electrosynthesized in boron trifluoride diethyl etherate (BFEE) and in the binary solvent system of BFEE and trifluoroacetic acid. Furthermore, structural characterization, molecular weight, ionization potentials and electron affinities, fluorescence properties, thermal stability, electrical conductivity, and morphology of PDBTO were minutely investigated. From FT?IR spectra and computational results, DBTO was probably polymerized through the coupling at C(3) and C(7) positions. The substitution of sulphonyl group in the fluorene ring increases its electron affinity considerably for improving electron injection/transport. Additionally, as-formed PDBTO was found to be a typical blue-light-emitter with maximum emission at 458 nm and concurrently exhibited good electroactivity and thermal stability.2. Low-potential electrochemical polymerization of a series of aromatic ethers in BFEE, e.g., 1,4-diphenoxybenzene (DPOB), 2,2'-dinaphthyl ether (DNE), led to successful deposition of a new class of electrically conducting proton-doped poly(aromatic ethers) thin films exhibiting good electroactivity and high thermal stability, whereas their sulfur analogues, diphenyl sulfide (DPS), and diphenyl sulfone (DPSO) were not eletropolymerizable. FT?IR spectra and computational results demonstrated that poly(1,4-diphenoxybenzene) (PDPOB) and poly(2,2'-dinaphthyl ether) (PDNE) were synthesized mainly through the coupling of DPOB at para?positions and DNE atα?positions of the naphthyl rings and C6, C6'positions, respectively. It was found that the electrodeposited poly(aromatic ethers) probably showed proton-doping nature similar to polyaniline based on FT?IR spectral results and conducivity investigation. As-formed PDPOB and PDNE were typical blue light emitters and highly fluorescent, with solution quantum yields of as high as 0.40 and 0.18, respectively.3. Polynaphthalene films with electrical conductivity of 10?3 S cm?1?10?1 S cm?1 were successfully electrosynthesized by direct anodic oxidation of 1,1'-binaphthyl (BN), 1,1'-bi-2-naphthol (BNO), and (S)-(-)-1,1'-bi-2-naphthol dimethyl ether (BNME) in CH2Cl2 containing additional BFEE. The resulting polymer films exhibited good redox activity and stability in different monomer-free electrolytes. Moreover, FT?IR spectra and quantum chemistry calculation results proved that the polymers were all synthesized mainly through the coupling of the monomers atα?positions of the naphthalene rings. Fluorescence spectral determination showed that the polymers were typical blue-light emitters with solution quantum yields of 0.17, 0.13, and 0.15, respectively. The substitution of hydroxyl and naphthyl groups did not change the emission wavelength of polynaphthalene (about 417 nm). Optical rotation determination showed that the conformation of BNME was maintained during the electrochemical polymerization process and the polymer exhibited greatly enhanced optical rotation value with main chain axial chirality compared with that of the monomer.4. High quality poly(9,10-dihydrophenanthrene) (PDHP) films with an electrical conductivity of 3.8×10?1 S cm?1 were synthesized electrochemically by direct anodic oxidation of 9,10-dihydro phenanthrene (DHP) at C(2), C(7) or C(3), C(6) positions in BFEE containing 10% concentrated sulfuric acid. The polymer obtained from this medium showed good electrochemical behavior and good thermal stability. Fluorescent spectral studies indicated that the polymer was a blue-light emitter with fluorescence quantum yield of 0.24.5. Crystalline nitro-group-substituted oligopyrene (ONP) film with fairly high electrical conductivity (1.25×10?1 S cm?1) and good thermal stability was electrochemically synthesized by direct anodic oxidation of 1-nitropyrene (NP) in BFEE. ONP films obtained from this medium showed good redox activity in both BFEE and concentrated sulfuric acid. FT?IR spectra and theoretical calculations showed that the electropolymerization of NP mainly occurred at C(3), C(6) and C(8) positions. As-prepared ONP emitted bicolored (blue and green) fluorescent light when excited at different wavelengths.6. A novel semiconducting polybenzanthrone (PBA), with relatively high electrical conductivity and excellent thermal stability, was successfully electrosynthesized by direct anodic oxidation of benzanthrone (BA) in acetonitrile solution containing Bu4NBF4 or BFEE acting as the supporting electrolyte. As-formed polybenzanthrone films showed good redox activity. FT?IR and 1H NMR spectral analyses and MALDI?TOF MS results, together with quantum chemistry calculations, proved that the polymer chains grew mainly via the coupling of the monomer at C(3) and C(11) positions. The fluorescence properties of polybenzanthrone were greatly improved in comparison with that of the monomer. Furthermore, polybenzanthrone dissolved in common organic solvents, with fluorescence quantum yields as high as 0.52, also emitted strong and bright green or yellow-green photoluminescence at excitation of 365 nm UV light.