Effect of counter-anion exchange on electrical conductivity of polypyrrole films

Abstract

The effect of counter anions on the electrical conductivity of polypyrrole films was investigated. Various anions including inorganic anions, sulfonates and carboxylates were introduced by counter-anion exchange reaction. The exchange reaction was performed by immersing a parent film in a propylene carbonate solution containing an anion to be exchanged. The rate depended not only on the kind of counter anion in the parent film but also on the kind of anion to be exchanged. The counter anion of a film containing PF 6 − was replaced completely by conjugate bases of various strong acids. Upon exchange, however, the electrical conductivity at room temperature remained substantially unchanged. The analyses of the films containing PF 6 −, ClO 4 − and TsO − by electron spin resonance, X-ray diffraction and specific gravity measurement suggested that some modification of the network structure occurs upon exchange. Although the apparent activation energy ( ΔE) of conductivity obtained by the Arrhenius plots changed slightly upon counter-anion exchange, the pre-exponential factor ( σ 0) remained substantially unchanged resulting in the preservation of room temperature conductivity.