Polyacetylenes doping

Electrically insulating films of polyacetylene, doped with iodine and sodium, became semiconductive (Shirakawa, MacDiarmid, Heeger, 1976). 

Note 2 The electric conductivity of a conjugated polymer is markedly increased by doping it with an electron donor or acceptor, as in the case of polyacetylene doped with iodine. 

C yields a polymer with 90% cis content polymerization at 100°C yields a polymer with >90% trans content. Polyacetylene, doped with an oxidant or a reductant, showed promise as a polymeric semiconductor [Chien, 1984], That promise was not realized because of the oxidative instability of polyacetylene and emergence of cheaper and more stable polymer systems (Sec. 2-14j). Various substituted acetylenes such as phenylacetylene have also been studied [Kanki et al., 2002 Misumi et al., 2000],... 

Microporous polypropylene has a poor conductivity (<10 ohm- cm- ), whereas the microporous polypropylene/polyacetylene laminate doped with iodine had a conductivity of 7.3 x 10 ohm cm", representing an improvement in conductivity of 10 . This final conductivity compares well with that of pure polyacetylene doped with iodine. 

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]. 

For Tsukamoto polyacetylene doped with FeCls, Ishiguro et al. [138] report a more compact structure than found before for Akagi polyacetylene. The authors specify a rectangular, face-centred projected chain array, 17.4 A, 6 = 9.8 A L =L =36 A. 

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. 

The first study of spin dynamics in a conducting polymer, polyacetylene doped with AsFb, was reported by Ncchtschein et al. in 1980, as shown in Figure 6.52 [143]. With (6.14) assuming cj>... 

Figure 11.119. Thermopower of PAiii, PMMA and PET blends with 40% PAni, and polyacetylene doped with MoClS (PAc) and iodine (9, 14 and 27 al.%1). The lines are fils for metallic difFusion thermopower. [Reproduced from ref 101 with kind permission of Elsevier.]...

Figure 13.22 Schematic variation of the conductivity of polyacetylene doped with iodine. The concentration is in moles of I2 per CH unit. The conductivity changes from that typical of an insulator to that associated with a metal...

Polyaniline, polypyrrole, polyparaphenylene and polyacetylene (doped with SO , HSOj), added to the positive paste as powders or fibres, enhance the formation process and increase the capacity of the cells. The amount of polymers added to the paste should be within the range 0.8—2.0 wt%. Higher polymer loads impair the mechanical stability of PAM and hence the life of the battery is shortened dramatically. Polymers disintegrate on overcharge. Polyaniline has proved to be most stable on battery overcharge. 

In order to understand the physical properties of polyacetylene doped with divalent ions, it is important to consider the theory of conductivity of polyacetylene doped with monovalent ions. One of the most unusual characteristics of polyacetylene is that small amounts of dopant ions give rise to enormous increases in electrical conductivity without causing any increase in the number of unpaired electrons. In fact, the small level of paramagnetism observed in pristine polyacetylene actually decreases on doping (8). This is in contrast to what occurs in traditional semiconductors, such as silicon, where dopants increase both conductivity and paramagnetism. An explanation has been offered by the soliton theory of conductivity (9,10). 

Similar to Kivelson s model. Chance and co-workers proposed interchain hopping for spinless conductivity in doped polyacetylene, doped poly(p-phenylene) and other doped polymers [102]. The mechanism accounts for the observed dopant concentration dependence of the conductivity in rans-polyacetylene and the observation of anomalously... 

FIGURE 15.49 The frequency-dependent dielectric function for highly oriented polyacetylene doped with perchlorate from Kramers-Rronig analyses of the reflectance spectra, (a) Light polarized perpendicular to polyacetylene chain direction, (b) Light polarized parallel to polyacetylene chain directions. (From Miyamae, T., Shimizu, M., and Tanaka, J., Bull. Chem. Soc. Jptu, 67, 2407, 1994. Reprinted from the Chemical Society of lapan. With permission.)... 

Pouget, J.P., et al. 1985. Structural study of polyacetylene doped with tetrahedral anions. Mol Cryst Liq Cryst 117 75. 

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