THE REVERSIBLE HYDROXIDE DOPING OF POLYPYRROLE - DELAY OF POLARON ANDMOBILE BIPOLARON INJECTION IN POLYPYRROLE BY H BONDING OF HYDROXIDE ANIONS

The reversible hydroxide-anion doping of polypyrrole (PPy) has been in vestigated by FT-IR, cyclic voltammetry, in situ conductivity and ESR techniques. FT-IR confirmed that the hydroxide anion substitutes the c ounteranion reversibly in doped PPy. The dopant hydroxide anion produc es a strong negative shift of the oxidation potential of PPy and doubl ing of the reversible charge. No similar effects are displayed in N-su bstituted PPys. In situ conductivity shows that the material becomes c onducting (up to 2 S cm(-1)) only after about 50% of the doping charge is passed. Similarly, the ESR signal is absent during the initial sta ges of charging, developing just before the onset of conductivity. The results indicate that the hydroxide anion stabilizes the positive cha rges in PPy by NH bonding. The interaction is so strong that fixed bip olarons are formed without the intermediate formation of polarons. Pol arons are produced only at higher charges with subsequent injection of mobile bipolarons and setting in of conductivity.