The electrochromic response of polyaniline and its copolymeric systems

Conducting polyaniline (PANI) and its copolymer films of poly(aniline-co-o-toluidine) (PAOT) and poly(aniline-co-o-anisidine) (PAOA) have been electrochemically synthesized. The optical and structural properties of PANI, PAOT and PAOA have been studied using UV-visible absorption and X-ray diffraction techniques. The X-ray diffraction study reveals a crystalline structure for PANI whereas it shows an amorphous structure for PAOT and PAOA conducting copolymer films. Moreover, the switching lifetime, applied voltage, cycle lifetime in the glass/ITO/conducting polymer/HCl/ITO/glass configuration of PANI, PAOA and PAOT have been experimentally investigated. Further, the current transient for coloration and discoloration has been analysed in order to understand the charge transport in conducting polymer and copolymeric systems. It has been shown that PAOA shows better electrochromic response (143ms) than PANI and PAOT systems. It is believed that the presence of the -OCH3 group in the PAOA copolymer facilitates the torsional angle between aniline and methoxy aniline. In addition, the effect of HCl acid molarity on the switching response of PAOA conducting copolymer films has been studied. (C) 1997 Elsevier Science S.A.