New analytical approach to the insulator–metal transition in conductive polyaniline

A new empirical formula describing the temperature dependence of the conductivity of polyaniline films in the metallic regime close to the insulator–metal transition at temperature below 30 K is deduced from the analysis of the temperature dependence of the reduced activation energy. Its elaboration is based on a careful study of electrical transport properties of camphorsulfonic acid-doped polyaniline (PANI(CSA)0.5) films, containing increasing amounts of triphenyl phosphate (TPP) plasticizer. The use of this three component system (polymer, protonating agent, plasticizer) and control of the amount of adsorbed water enable precise tuning of the electrical transport properties in the solution cast films, in this manner providing the set of experimental data, covering the insulating, critical and metallic regimes, necessary for the elaboration of the proposed new empirical formula.