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, 1H 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 × 10−3 S cm−1 to 8.1 × 10−3 S cm−1 at room temperature, and exhibited good thermal stability in nitrogen up to 337–356 °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.