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Role Of The Dopant Counter-ions In The Transport And Magnetic Properties Of Disordered Conducting Polymers
Published 1994 · Materials Science
Summary form only given. Disordered conducting polymers like polypyrroles or even some of the polyanilines contain generally short electroactive chains with conjugation lengths of a few ten monomers. Most of the electronic properties of these materials cannot be really understood in terms of quasi-one-dimensional models. i) Why in the fully doped materials the number of Curie spins is always lower than half the number of segments? ii) Why these disordered materials exhibit a Pauli-like component in their spin- susceptibility? iii) Why are the conductivities of all the fully doped materials roughly of the same order of magnitude (0.1 to 10 S/cm) independent of the micro structures and chain lengths? iv) Why the same value of the conductivity is found in thin films of doped oligomers? All these questions can be resolved if the interactions between the carriers and the dopant counter-ions are properly accounted for. It is then possible to derive a new interpretation of the spin-charge relation and of the so-called Curie and Pauli contributions to the susceptibility. Moreover the dopant ion is ultimately responsible for 3D localization through formation of transverse bipolarons connecting neighbour chains via enhanced tunnelling probability close to a counter-ion. Thus the hopping process through the disordered material can be revisited in relation with these new concepts.