Stability of polyaniline synthesized by a doping-dedoping-redoping method

Stability, including thermal stability, conductivity stability in air and after thermal treatment (100-200 degrees C), of the polyaniline (PANI) films synthesized by a doping-dedoping-redoping method was investigated. It was found that thermogravimetric analysis (TGA) curves undergo three steps: loss of water or solvent, dedoping and decomposition, and those depend on the counterions. Compared with PANI films doped with camphor sulfonic acid (CSA) in m-cresol, the thermal stability of the doped PANI films is improved by the new method, and thermal stability in the order of PANI-H3PO4 > PANI-p-TSA > PANI-H2SO4 > PANI-HCl, PANI-HClO4 > PANI-CSA was observed. The conductivity of the doped PANI films at room temperature was reduced after thermal treatment, and it is dependent of the counterions. It was found that the conductivity stability of PANI-p-TSA and PANI-CSA is the best below 200 degrees C. When the doped PANI films were placed in air, their conductivity decrease slowly with time due to deproton, and also depends on the counterions. (C) 1999 John Wiley & Sons, Inc.