Electrochemistry, morphology, thermoelectric and thermal degradation behaviors of free-standing copolymer films made from 1,12-bis(carbazolyl) dodecane and 3,4-ethylenedioxythiophene

A copolymer based on 1,12-bis(carbazolyl)dodecane (2Cz-D) and 3,4-ethylenedioxythiophene (EDOT) was electrochemically synthesized in dichloromethane containing 0.1-M tetrabutylammonium tetrafluoroborate. Cyclic voltammetry, Fourier-transform infrared, morphological and elemental analyses confirm that the resultant polymer is a copolymer rather than a composite or a blend of the two homopolymers. The copolymer exhibits good redox activity and high electrochemical stability. In contrast with powdered poly(3,4-ethylenedioxythiophene) (PEDOT), the copolymer formed in this study exists in a free-standing film state, and it has a higher thermal stability and better mechanical properties. Moreover, the copolymer films emit blue light, depending on the monomer feed ratios. The thermoelectric properties of the copolymer films were also investigated. Because the 2Cz-D/EDOT feed ratios were different, the electrical conductivities of the obtained copolymer films were improved to varying degrees compared with that of the poly(1,12-bis(carbazolyl) dodecane) (P2Cz-D) film. The highest obtained electrical conductivity was 0.6 S cm(-1), four orders of magnitude higher than that of P2Cz-D (2.7 x 10(-5) S cm(-1)). The Seebeck coefficients of the copolymer films were also modified compared with that of P2Cz-D. All of these enhanced properties will be beneficial to the potential applications of these materials in polymer optoelectronics or as organic thermoelectric materials. Polymer Journal (2011) 43, 531-539; doi:10.1038/pj.2011.26; published online 27 April 2011