Conducting Charge-Transfer Organic Polymers electrical conductivity

Much work has been undertaken to modify electrode surfaces with films which are themselves conducting. The most promising approaches involve organic charge transfer and radical ion polymers. Coordination chemistry has, to date, played little part in this work (a good recent review is available),67 but one example relating to ferrocene chemistry can be quoted. In this example a well known electron acceptor, 7,7, 8,8 -tetracyanoquinodimethane (TCNQ 27), is modified and incorporated into polymer (28) in which the iron(II) of the ferrocene unit is the electron donor. The electrical conductivity of such a film will depend on partial electron transfer between ion and TCNQ centres as well as on the stacking of the polymer chains. The chemistry of other materials, based on coordination compounds, which have enhanced electrical conductivity is covered in Chapter 61. 

Nalwa HS, "Handbook of Organic Conductive Molecules and Polymers", Vol. 1, "Charge-Transfer Salts, Fullerenes and Photoconductors" Vol. 2, "Conductive Polymers Synthesis and Electrical Properties" Vol. 3, "Conductive Polymers Spectroscopy, Photo-Physics and Applications" Vol. 4, "Conductive Polymers Transport and Physical Properties", Wiley, Chichester, 1997. 

Organic polymers that possess the electronic, magnetic, and optical properties of metals are known as conductive polymers (CPs). Because of their conjugated u electron backbones, they can be oxidized or reduced more easily and more reversibly than conventional polymers with charge-transfer agents, also commonly called dopants, a term borrowed from condensed matter physics. While retaining some of the mechanical properties of polymers, they do not melt or dissolve in common organic solvents, a major impediment to their widespread commercialization in the same manner as traditional plastics. The same electronic structure that confers electrical conductivity to these polymers also contributes to their intractability and instability. 

Some aspects of computational quantum chemistry applied to the analysis of the electronic structure of polymers are reviewed in connection with the timely trends observed in their electrical and optical properties. The paper is organized as follows after an introduction (Section 36.1), the basic theory of the quantum chemical methodologies as applied to periodic chains is summarized (Section 36.2). Several fields of applications are then presented photoelectron spectra (Section 36.3), conducting and semiconducting conjugated polymers (Section 36.4), hnear and non-linear optical properties (Section 36.5) and the role of charge transfer in organic chains (Section 36.6). Possible developments for the near future are also sketched. 

Finally it should be remembered that all electrically conducting organic materials are due to the various dopant charge-transfer complexes, and coming back to the roots—in the 60s—polymer CT-complexes are found to be electrically conducting materials with up to lO S/cm [6]. 

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