Conducting Polymers. VII. Effect of Doping with Iodine on the Dielectrical and Electrical Conduction Properties of Polyaniline

The oxidative chemical polymerization of aniline monomer in acidic aqueous media by using potassium dichromate as unconventional initiator was carried out at room temperature based on two different comparative methods. In the first method, in situ polymerization of polyaniline, polymerization was carried out in the presence of iodine solution (PANI/I2-In). In the second method, ex situ polymerization, after complete polymerization polyaniline was doped with iodine (PANI/I2-Ex). FTIR, UV measurements, and TGA analysis for undoped polyaniline (PANI), iodine doped polyaniline (PANI/I2-Ex), and iodine doped polyaniline (PANI/I2-In) show that iodine doping process occurred at the quinoid units in the polyaniline backbone of (PANI/I2-Ex) while iodine doping occurred at benzenoid units in polyaniline, in addition the iodination occurred at the rings of polyaniline backbone of (PANI/I2-In.). The data extracted from the XRD patterns shows the crystalline nature of synthesized samples and particles sizes are in the range 37–42 nm. The activation energies of thermal degradation of polyaniline or iodine doped polyaniline were determined from the TGA thermogram for PANI, (PANI/I2-In), and (PANI/I2-Ex) are 24.1, 43.4, and 44.19 KJ/mol, respectively. Doping of PANI with iodine enhances the ac conductivity of PANI whatever the method of doping, The room temperature values of σac measured under test frequency 100 kHz are found to be 6×10−5, 2.5×10−4, and 1×10−3 Ω−1.m−1 for PANI, (PANI/I2-In), and (PANI/I2-Ex), respectively.