The mechanism of the electrosynthesis of poly(3-butylthiophene) (PBuT) was
studied by cyclic voltammetry and potential step methods in comparison with
polybithienyl. The anodic oxidation polymerization of the 3-butylthiophene
underwent two steps: oligomer formation and further polymerization to form
the polymer. The doping level of the PBuT increases with the cycle number
of the potential sweeps during polymerization. The current responses to the
potential steps indicate a nucleation and nuclei growth process which is r
epeated layer to layer. The differential capacity (Cd) and photocurrent wer
e measured at the PBuT films in the aqueous electrolyte solution. The C-d(-
2) VS. E plot shows two regions of linearity, one with a negative slope and
the other with a positive slope in different potential regions, which give
the same flat-band potential. This indicates that the PBuT film exhibits b
oth p-type and n-type features of a semiconductor at differrent potential r
egions. The cathodic photocurrent spectrum was analysed by the (j(ph)h nu)(
2/n) vs. h nu plots, giving band gap energies of 2.41 eV for n = 1 and and
2.01 eV for n = 4.