The temperature dependence of the dc conductivity of electrochemically polymerized films of polypyrrole, poly͑N-methyl pyrrole͒ and their copolymers, poly͑N-methyl pyrrole-pyrrole͒, having different percentage of BF 4 Ϫ ions has been investigated in the temperature range 77-350 K. The observed behavior could be explained in terms of Mott's variable range hopping model involving a single phonon process. The estimated values of polaron radius yield the realistic values of density of states at the Fermi level which are in good agreement with the values reported earlier for other polyconjugated systems.

The current–voltage characteristics of Schottky junctions formed by using aluminum on polypyrrole, poly(N-methyl pyrrole) and the copolymer poly(N-methyl pyrrole–pyrrole) have been investigated. The formation of the junctions has been confirmed by capacitance–voltage characteristics and Chot plots. The results have been explained on the basis of thermionic emission theory.

Alternate and direct current conductivity of conducting polyaniline dispersed with poly vinyl alcohol and blended with methyl cellulose

The alternating current (ac) conductivity [σm(ω)], dielectric constant (ε′) and loss (ε″) of polypyrrole (PPY), poly(N-methyl pyrrole) [P(NMPY)] and their copolymers; poly(N-methyl pyrrole–pyrrole [P(NMPY–PY)] have been measured in the frequency range 102–106 Hz and in the temperature range 77–350 K. At 77 K, the ac conductivity can be expressed by the relation; σac=Aωs where the slope s lies in the range 0.72–0.81 for these three polymers and decreases with increase in temperature. The well-defined loss peaks, whose magnitude decreases with the increase in frequency, have been observed in the temperature region where the measured ac conductivity approaches the direct current (dc) conductivity. These loss peaks have been associated with the movement of charge carriers in these polymeric films. The dc conductivity has also been measured in the temperature range 77–350 K and an attempt has been made to correlate it with dielectric data.

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