Polyaniline

Is polyaniline really a metal?

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Polyaniline (PANI) is the oldest artificial polymer, which is known to be conducting. The emeraldine form of PANI has two quinoid rings and the leucoemeraldine form has one quinoid ring in an eight ring repeat unit, as it is shown in the following figure.

Leucoemeraldine is the completely reduced form of PANI.
The charge carriers produced by adding an acid are paramagnetic. Acid doped PANI shows a paramagnetism, which temperature dependence is often described as a mixture of Curie  and Pauli paramagnetism. Well prepared PANI samples doped with camphersulfonic acid show pure Pauli paramagnetism as shown in the following figure.



This behaviour is usually considered to be a proof for the metallic properties of that samples. From a chemical point of view we know that there is an equilibrium between non oxidized, double oxidized and single oxidized spin bearing polymer segments. Each concentration is determined by this equilibrium constant. This equilibrium constant is also temperature dependend what means that all species involved in that equilibrium have a temperature dependent concentration. Also on this basis the temperature independent susceptibility can be well explained. These simple facts have not been considered before.

A more detailed version can be found here.

Contact

Prof. Lothar Dunsch