EFFECT OF SYNTHESIS TEMPERATURE ON THE STRUCTURE, DOPING LEVEL AND CHARGE-TRANSPORT PROPERTIES OF POLYPYRROLE

Polypyrrole perchlorate was chemically synthesized at various temperatures and the resulting polymers were investigated by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and conductivity measurements. A correlation between conductivity, doping level and synthesis temperature was observed. The doping level of the polymer is higher when the synthesis is conducted at lower temperature. In addition, polypyrrole synthesized at lower temperature exhibits longer conjugation length, fewer structural defects, higher charge-carrier hopping frequency and higher conductivity. Furthermore, the results of this study indicate that the positive charges of doped polypyrrole are preferentially localized on the nitrogen atoms which are adjacent to the doping anions, as opposed to being uniformly delocalized along the polymer backbone.