Effect of oxidants on chemical synthesis and properties of poly(3,4-ethylenedithiathiophene)

The effects of different oxidants, such as FeCl₃, (NH₄)₂S₂O₈, H₂O₂, Ce(SO₄)₂, and (NH₄)₂Ce(NO₃)₆, on the chemical oxidative polymerization of 3,4-ethylenedithiathiophene (EDTT) were investigated in H₂O, CH₃CN or H₂O/CH₃CN. It has been found that H₂O₂ can hardly give visible polymer deposits until catalytic amount of FeCl₃ was added. Ce(SO₄)₂ and (NH₄)₂Ce(NO₃)₆ can give relatively rapid rates of polymerization, while poly(3,4 ethylenedithiathiophene) (PEDTT) obtained using FeCl₃ and Cerium(IV) salts presented much higher yields. Moreover, properties of PEDTT were also greatly influenced by oxidants. (NH₄)₂S₂O₈ and (NH₄)₂Ce(NO₃)₆ can give soluble polymers in N,N dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), and PEDTT synthesized using FeCl₃ showed the highest electrical conductivity values (about 0.1~0.2 S cm^-1). The decomposition of PEDTT prepared using FeCl₃/H₂O₂starts at 490 K, which was higher than those using (NH₄)₂S₂O₈ and Cerium(IV) salts. FT-IR spectra measurements indicated the formation of PEDTT molecular chains via α, α coupling of thiophene rings. UV, fluorescence and thermal properties of PEDTT were also characterized.