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

The effects of different oxidants, such as FeCl
₃
, (NH
₄
)
₂
S
₂
O
₈
, H
₂
O
₂
, Ce(SO
₄
)
₂
, and (NH
₄
)
₂
Ce(NO
₃
)
₆
, on the chemical oxidative polymerization of 3,4-ethylenedithiathiophene (EDTT) were investigated in H
₂
O, CH
₃
CN or H
₂
O/CH
₃
CN. It has been found that H
₂
O
₂
can hardly give visible polymer deposits until catalytic amount of FeCl
₃
was added. Ce(SO
₄
)
₂
and (NH
₄
)
₂
Ce(NO
₃
)
₆
can give relatively rapid rates of polymerization, while poly(3,4 ethylenedithiathiophene) (PEDTT) obtained using FeCl
₃
and Cerium(IV) salts presented much higher yields. Moreover, properties of PEDTT were also greatly influenced by oxidants. (NH
₄
)
₂
S
₂
O
₈
and (NH
₄
)
₂
Ce(NO
₃
)
₆
can give soluble polymers in N,N dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), and PEDTT synthesized using FeCl
₃
showed the highest electrical conductivity values (about 0.1~0.2 S cm
^-1
). The decomposition of PEDTT prepared using FeCl
₃
/H
₂
O
₂
starts at 490 K, which was higher than those using (NH
₄
)
₂
S
₂
O
₈
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.