Structure and properties of solid-state synthesized poly(3′,4′-ethylenedioxy-2,2′:5′,2-terthiophene)

A polyterthiophene derivative: poly(3',4'-ethylenedioxy-2,2':5'.2 ''-terthiophene) was synthesized by solid-state oxidative-polymerization of 3',4'-ethylenedioxy-2,2':5',2 ''-terthiophene (TET) in various ratios of oxidant (FeCl3) to the monomer (TET). The resulting polymers were characterized by FT-IR, H-1 NMR, TEM, SEM, UV-vis-NIR, GPC, X-ray diffraction, EDX, CV, galvanostatic charge-discharge, as well as TGA and conductivity measurements. The results showed that the as-made poly(TET)s were partially in doped state with a conductivity ranging from 2.1 x 10(-3) S cm(-1) to 8.1 x 10(-3) S cm(-1) at room temperature, and exhibited good thermal stability in nitrogen up to 337-356 degrees C. The poly(TET)s showed a similar UV-vis absorption peak at 462 nm in acetonitrile. In addition, as-made poly(TET)s had low molecular weight ranging from 3300 to 3500 with microstructured morphology including nanorodes and nanofibers, and presented one redox couple at 1.1-1.2 V(ox) and 0.6-0.7 V(re) in 0.1 M Et4NBF4 acetonitrile solution. A moderate specific capacitance of 71 F g(-1) for poly(TET) modified graft electrode was obtained within the potential range of -0.2 V to 0.5 V in 1 M H2SO4 solution. X-ray diffraction results imply the enhanced crystallinity of poly(TET)s, indicating the existence of crystalline phase in polymer matrix. Furthermore, the comparison of results from every measurement indicated that the [FeCl3]/[TET] ratio strongly affects the morphology of the poly(TET), and the fibrillar growth tendency of poly(TET) was observed with the increase of the [FeCl3]/[TET] ratio, and long-length fibrillar morphology occurred in the highest [FeCl3]/[TET] ratio. (C) 2009 Elsevier B.V. All rights reserved.