MEMORY EFFECT OF ELECTRICAL-CONDUCTIVITY UPON THE COUNTER-ANION EXCHANGE OF POLYPYRROLE FILMS

The memory effect of electrical conductivity upon counter-anion exchange was investigated with polypyrrole films. Various inorganic anions and sulfonates were introduced to a film containing PF6- by the exchange of counter anions. The room-temperature conductivity remained substantially unchanged upon the exchange. The inversion of temperature dependence of conductivity, which was observed specifically with the parent film below 20 K, was also preserved. The memory effect suggested that the conductivity of the film with a polymer-chain network of the same origin is independent of the kind of counter anion. The marked dependence on the counter anion observed in the as-grown films was assumed to be due to the structural difference of the polymer-chain network.