ON THE PH INFLUENCE ON ELECTROCHEMICAL PROPERTIES OF POLY(PYRROLE) AND POLY(N-METHYLPYRROLE)

The electrochemical behavior of poly(pyrrole) doped with chloride (PPy /Cl) and dodecylsulfate (PPy/DS) ions as, well as of poly(N-methylpyrr ole) doped with perchlorate anions (PMPy/ClO4) was studied in aqueous electrolyte (KCl) solutions (pH 0.5 to 7). The results indicate that t he pH efiPct is dependent on polymer/dopant system properties, althoug h in general the pH change moatly affects the polymer by the change of solution redox potential. Although the studied polymers exhibit diffe rent formal potential and ion-exchange properties, open circuit potent ials of these films were quite similar. The slope of the open circuit potential dependence on pH was the highest: fur PPy/Cl, but still much below the value expected for the H+ exchange process. The high sensit ivity of PPy/Cl films for the pH changes was also observed in impedanc e measurements. Results obtained for the PPy/Cl system indicate that a cidfication of the solution favors lower charge transfer impedances. T he: results of voltammetric studies indicate that conditioning of the PPy/Cl layer in neutral solution is accompanied with deprotonation of the polymer film. This effect was less pronounced for the PPy/DS layer s probably due to the inhibiting properties of the surface active dopi ng anions, and was not observed for PMPy/ClO4 films. This suggests tha t hydrogen atom connected with nitro rn atom is involved in the discus sed processes.