Novel Conducting Polymers From Thiophenes And Fused-ring Aromatic Compounds Via Electrochemical Copolymerization

Since discovery of the first conducting polymer (i.e. polyacetylene), conducting polymers (CPs) have received considerable attention by virtue of their especial physical and electrochemical properties and vast application prospects. Up to date, CPs have potential applications in electronic devices (e.g. Schottky rectifier, field-effect transistor, light emitting diode and solar cell), electromagnetic interference shielding and microwave absorbing materials, rechargeable batteries and supercapacitors, electrochromic devices, sensors and artificial muscles. Because of their relatively higher electrical conductivities and good environmental stability, polythiophenes as one kind of conventional and representative CPs have been of significant interest for their potential applications. Moreover, considerable efforts have been focused on the syntheses and properties of poly(fused-ring aromatic compounds), as these polymers usually possess wideπ-conjugated structure and excellent fluorescent properties. As well known that electrochemical polymerization has been a useful and widely applied technology for the electrosynthesis of CPs. In addition, CPs with various properties can be achieved via adjusting the electronic character of theπ-orbit along the neutral polymer backbone, including main chain and pendant group structural modification, copolymerization and composite. In this paper, novel conducting copolymers based on thiophenes and some fused-ring aromatic compounds were electrosynthesized. The synthesis conditions, structures and properties of as-formed copolymers were studied in detail.1. In the binary solvent system of boron trifluoride diethyl etherate (BFEE) and acetonitrile (ACN), thiophene (Th) and 3-methylthiophene (3MeT) were electrochemically copolymerized with benzanthrone (BT), respectively. The as-obtained copolymer showed good electrochemical activity and stability, high mechanical property, and fine fluorescence property, which was relevant with the initiate monomer feed ratio. Compared with that of polybenzanthrone (PBT), the electrical conductivities of the copolymers were relatively higher and the mechanical properties of the copolymer films were improved. 2. Thieno[3,2-b]thiophene (TT) was successfully synthesized chemically and then electropolymerized in BFEE, ACN and dichloromethane (DCM) systems, respectively. In BFEE, the as-obtained polythieno[3,2-b]thiophene (PTT) was free-standing film with high mechanical property, good electrochemical activity and stability, and high thermal stability. Furthermore, PTT can be used as a thermoelectric material with the highest electrical conductivity of 1.5 S cm^-1, Seebeck coefficient of 85μV K^-1 and figure of merit (ZT) of 2.5×10^-3.3. TT and 1,12-bis(carbazolyl)dodecane (2Cz-D) were electrochemically copolymerized in the binary solvent system of BFEE and DCM. The as-formed copolymer was free-standing film with smooth and compact surfaces and high mechanical property. Cyclic voltammograms (CVs) indicated the high electrochemical stability and good redox reversibility of the conducting copolymer films. Additionally, the obtained copolymer was still a good blue-light emitter as well as poly(1,12-bis(carbazolyl)dodecane) (P2Cz-D). The thermoelectric properties of the resultant copolymer films were improved compared with those of the respective homopolymers and affected by the initiate monomer feed ratio.4. A novel conducting copolymer was electrochemically synthesized from 3,4-ethylenedioxythiophene (EDOT) and 2Cz-D in DCM system. CVs suggested the high electrochemical activity and stability of the resulting copolymer films. Obtained copolymers were all in free-standing film state with smooth and homogenous surfaces, high mechanical properties, and high thermal stability. Similar with P2Cz-D, as-formed copolymer films were good blue-light emitters. The electrical conductivities and Seebeck coefficients of the copolymer films were both improved compared with those of P2Cz-D films. The quality of the copolymer films was significantly enhanced in comparison with that of the powdered poly(3,4-ethylenedioxythiophene) (EDOT).