Polythiophenes dopant effects

Let us suppose an infinite nondegenerate polymer chain (e.g., polythiophene) doped heavily with electron acceptors. At a high dopant content, the polymer-chain structure and electronic structure of the doped polymer are radically different from those of the intact polymer. As typical cases, we will describe two kinds of lattice structures of doped polythiophene (dopant content, 25 mole% per thiophene ring) a polaron lattice and a bipolaron lattice. They are the regular infinite arrays of polarons and bipolarons. The schematic polymer-chain structures are shown in Figure 4-16. Band-structure calculations have been performed for polaron and/or bipolaron lattices of poly(p-phenylene) [124], polypyrrole [124], polyaniline [125], polythiophene [124, 126], and poly( p-phenylenevinylene) [127], with the valence-effective Hamiltonian pseudopotential method on the basis of geometries obtained by MO methods. The schematic electronic band structures shown in Figure 4-17... 

Since the initial discovery of polyacetylene doping by FeClj [92], ferric chloride still remains one of the most popular dopants for conjugated polymers. In addition, it is a very efficient oxidizing/polymerizing agent for the preparation of polypyrrole, polythiophene and their derivatives [32,84]. The most extensive Mbssbauer effect studies have therefore been carried out for FeCl, doped polymers. 

Research is ongoing in the field of ECPs in order to discover various new polymers in this field, which shows the increased demand for these specialty conjugated polymers. It is necessary to use effective and stable dopants with the conducting polymers for the enhancement of their properties [1-4]. Conjugated polymers with good electronic conductivity have opened the door to various electronic devices. Various ECPs used nowadays are polyaniline, polypyrrole, polythiophene, polyacetylene, and their derivatives. The major advantages of these polymers are good electronic... 

In relation to the specific effects described above, electrochemically synthesized polythiophenes also exhibit interesting morphologies [17, 30, 31, 33]. The STM images again indicate that the (super)helical structures are involved. The cooperation between the host polymers and dopant ions seems responsible for those structures as well. In this context, Hotta [37] pointed out that rapid deposition of the polymer chains that follows umnediately after the electrochemical generation of those polymers may well lead to rather unusual crystal structures. 

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