Doped conjugated polymers structures

Table 6.10 Structures and Conductivities of Doped Conjugated Polymers...

Table 2 shows the present state-of-the-art for the electrical conductivity of doped conjugated polymers. The magnitude of the electrical conductivity in polymers is a complex property determined by many structural aspects of the system. These include main-chain structure and 7T-overlap, molecular... 

Here I would like to mention attempts of synthesizing carbynoid structures by Kijima et al. [6,9] using electrochemical approach. Cathodic electrolysis of a solution of poly(vinylidene fluoride) (PVDF) in DMF containing tetrabutylammonium perchlorate, and tert-butyl alcohol as a mediator was found to produce -doped conjugated polymers consisting of 76% of poly(fluoro-acetylene) and 24% of carbynoid moieties [6] (Scheme 12.7) ... 

A further study of the symmetry aspects of the superlattices of columnar structures in doped conjugated polymers (commonly referred to as channel structures in polyacetylene studies) has been presented by Heiney et al. [115]. The authors discuss the effects of broken symmetries of either the 2D-projected lattice or the columnar building blocks (called motifs ... 

Heiney, P.A., et al. 1991. Channel structures in alkali-metal-doped conjugated polymers—broken symmetry 2-dimensional intercalation superlattices. Phys Rev B 44 2507. 

ELECTRICAL BEHAVIOR OF POLYMERS 785 Table 14.6 Structures and conductivity of doped conjugated polymers (59)... 

Metallic polymers can be obtained by (a) pyrolysis of insulating or semiconducting polymers (b) incorporation of metallic particles (c) action of electron donors and acceptors on conjugated polymers and (d) producing half-filled band structures, (a) and (b) are the principal routes to commercial products (see Sections 22.5.1 and 22.5.2). The discovery of metallic conductivity in doped conjugated polymers is relatively recent, but has been subject to intense activity (see Section 22.4). So far, a linear carbon-backbone polymer with intrinsic metallic behaviour has not been reported. This stems from the fact that some structural deformation can apparently always produce a semiconducting state of lower total energy. 

Conjugated polymers are generally poor conductors unless they have been doped (oxidized or reduced) to generate mobile charge carriers. This can be explained by the schematic band diagrams shown in Fig. I.23 Polymerization causes the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the monomer to split into n and n bands. In solid-state terminology these are the valence and conduction bands, respectively. In the neutral forms shown in Structures 1-4, the valence band is filled, the conduction band is empty, and the band gap (Eg) is typically 2-3 eV.24 There is therefore little intrinsic conductivity. 

Conjugated polymers doped with C60 become p-type semiconductors [305,306] some LB films of two polyalkylthiophenes mixed with arachidic acid and doped with C60 have been prepared [307]. The films of polyalkylthiophene + arachidic acid -l- C60 (spread from mixtures of 1.0 0.33 0.1 ratio) on ITO glass had a well-defined layer structure, as confirmed by x-ray diffraction. The bilayer distance obtained from the Bragg equation was 5.6 nm, the same as for arachidic acid LB films. Since the films were spread on subphases containing... 

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