Polyaniline: Protonic Acid Doping to the Metallic Regime

Abstract

“Polyaniline” has been synthesized in various forms both chemically and electrochemically in aqueous media. The quinoid-benzenoid-diimine form, an insulator, is doped by dilute aqueous protonic acids to the metallic regime ([sgrave] ∼ 5 ohm⁻¹cm⁻¹; compressed pellet) to give the corresponding iminium salt. The polymer is not oxidized during the doping process. This represents a new type of p-doping phenomenon in a conducting polymer. Both these forms of polyaniline are stable in the presence of air and/ or water. The doping process is reversed by treatment with aqueous alkali. The mechanism by which doping occurs is discussed.