Polyparaphenylene conductivity

In 1979, the formation of conductive polypyrrole films by the electrochemical oxidation of pyrrole was reported for the first time This work has stimulated intense and fruitful research in the field of organic conducting polymers. Further important conductive polymers are polythiophene, polyaniline and polyparaphenylene. The development and technological aspects of this expanding research area is covered... 

Table 5.3 Examples of electronically conducting polymers, y is the level of electrochemical doping and k is the maximum electrical conductivity. Except for poly acetylene and polyparaphenylene, only p-doping is considered... 

Solitons are considered to be important defect states in these conjugated polymers (see Fig. 6.48). It has however been shown that correlation energy is the more important factor in giving rise to the energy gap in (CH) (Soos Ramasesha, 1983). Other polymers related to polyacetylene are polythiophene, polypyrrole, poly-phenylenesulphide, and polyparaphenylene (Section 3.3). Extensive measurements on doped polyacetylenes have been reported in the last five years and these materials, unlike other conducting polymers such as (SN), seem to have good technological potential. 

The synthesis and characterization of polyacetylene (PA) provided new incentive for understanding 7r-electronic spectra, electron-phonon interactions and electronic correlations[l, 2, 14]. The electrical conductivity of chemically doped PA rivals that of metals. Families in Fig. 2 such as polydiacetylenes (PDAs), poly thiophenes (PTs), cr-conjugated polysilane (PSs) and polyparaphenylene vinylene (PPVs), among... 

Conductive polymers, i.e., polyaniline, polypyrrole, polyparaphenylene, and polyacetylene, in the form of powders or fibres. These polymers are added to the positive paste. The maximum amounts of these additives should not exceed a few percent. To date, there are no data that indicates wide application of these polymers by the battery industry. 

Polymeric tubes for clad lead-acid battery plates have been made from intrinsically conductive polymers [19] by weaving fibres of polypyrrole, poly(phenylene vinylene), or polythiophene of several hundred microns in thickness. Polyaniline [20] as well as polypyrrole, polyparaphenylene, and polyacetylene doped with anions (C104, FeCl, AsFj, sol", and HSO4) have also been added as 1.15pm powders or fibres to positive pastes to improve capacity [21]. 

An important part of Andre and Bredas s work during the 1980s was to analyze and extend the soliton, polaron and bipolaron models to a number of cases [54] polypyrrole, polyparaphenylene, poly anilines, polythiophenes, etc. More details on the theory of conducting polymers can be found in specialized monographs [55]. 

Matrix polymer and an electrically conducting thermotropic liquid-crystal polymer, LCP matrix PO, EPR, CPE, CSR, PS dispersed PANI, PAc, PPy, poly(3-undecylthiophene), poly(3-dodecylthiophene), or polyparaphenylene Ho Levon, 1995... 

By contrast, the ECP must have conjugated rigid-rod macromolecules. Several such polymers show high electrical conductivity (usually after doping), viz. polyacetylene (PAc), polyaniline (PANI), polypyrrole (PPy), polyparaphenylenes (PPP), or poly-3-octyl thiophene (POT). The resins are expensive, difficult to process, brittle and affected by ambient moisture, thus blending is desirable. For uniaxially stretched fibers the percolation threshold is 1.8 vol%, hence low concentration of ECP (usually 5-6 vol%) provides sufficient phase co-continuity to ascertain conductivity similar to that of copper wires (see Table 1.79). 

Finally an LDA calculation was also performed for a polyparaphenylene (PPP) helix.100 This conducting polymer (if doped) is quite interesting for its applications in light emitting diodes101 (especially because it emits blue light102), in field-effect transistors103 and in non-linear optical devices.104... 

The microwave behaviour of numerous conductive polymers has also been published such as polyaniline (lMHz-20GHz) [41] polypyrrole [42,43] polyparaphenylene [44a] polythiophene [44a,b] poly-p-phenylene-benzobis-thiazole [45] poly-(p-phenylene vinylene) [46]. 

In polyparaphenylene, a soliton wave is not possible because the two phases, quinoid and aromatic, are not of the same energy, which excludes free motion. A double defect is possible though, a bipolaron. Such a defect represents a section of the quinoid stmcture (in the aromatic-like chain), at the end of which we have two unpaired electrons. The electrons, when paired with extra electrons from donor dopants or when removed by acceptor dopants, form a double ion (bipolaron), which may contribute to electric conductance. 

FIGURE 5.8. Structures of some common doped conductive polymers, each projected on a plane normal to the direction of the polymer chains. Cross-hatched circles indicate dopant ions, (a) The square channel structure of potassium-doped polyacetylene (other alkali-doped PA lattices show similar structures),(b) lithium-doped polyparaphenylene, (c) potassium-doped ppp,(ii3) AsFs-doped PPR In (d) the dopant species, represented by x, are probably... 

J. E. Bredas, B. Themans, J. G. Fripiat, J. M. Andre, R. R. Chance, Highly conducting polyparaphenylene, polypyrrole and polythiophene chains - an ah initio study of the geometry and electronic structure modifications upon doping, Physical Review B 1984, 29, 6761. 

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