STRUCTURE-CONDUCTIVITY RELATIONSHIPS OF IODINE-DOPED POLYANILINE

Polyaniline, synthesized by using potassium dichromate as the oxidant, was doped with iodine in order to increase its electrical conductivit y. The iodine-doped polyanilines attained a conductivity of 1.83 x 10( -3) S/cm, which was about eight orders of magnitude greater than that of intrinsic polyaniline. The iodine-doped polyanilines did not absorb moisture readily when compared to the protonic-acid-doped polyaniline s. Fourier transform infrared (FTIR) and x-ray photoelectron spectrosc opy (XPS) results indicated that iodine-doping reactions occurred at t he N-atoms in the quinoid structural units of the polyaniline molecula r chains and consequently formed the charge transfer complexes. The io dine in the iodine-doped polyanilines existed mainly in the forms of I -3(-) and I-5(-) anions. As the doping level increased, the relative c ontent of I-5(-) anions increased. Thermogravimetric analysis (TGA) re sults showed that there was about 6 wt % of iodine strongly bonded to the polyanilines since they would not evolve even at the structural de composition temperatures of the polymer backbones. Wide-angle x-ray di ffraction spectroscopy (WAXD) results revealed that the intrinsic poly aniline was an amorphous polymer but the regularity of polyaniline cha ins increased after iodine-doping. The iodine-doped polyanilines also showed a decrease in thermal stability. (C) 1997 John Wiley & Sons, In c.