Poly iodine doped

For poly(phenylacetylene) doped with acceptor iodine molecules the long wavelength bands at 940 nm were ascribed to CT complexes [178, 179]. The band model with trap controlled conductivity was used to the photoconductive... 

As discussed earlier, substitution onto the polyacetylene chain invariably has a deleterious effect on dopability and conduction properties. At the same time the stability tends to improve. Masuda et al.583) studied a large range of substituted polyacetylenes and found that stability increased with the number and bulkiness of the substituents, so that the polymers of aromatic disubstituted acetylenes were very stable, showing no reaction with air after 20 h at 160 °C. Unfortunately, none of these polymers is conducting. Deitz et al.584) studied copolymers of acetylene and phenylacetylene they found that poly(phenylacetylene) degrades even more rapidly than does polyacetylene and that the behaviour of copolymers is intermediate. Encapsulation of the iodine-doped polymers had little effect on the degradation, which is presumably at least in part due to iodination of the chain. 

The electrochemical behavior of poly(ferrocenylsilanes) has been studied at three levels—in solution by cyclic voltammetry, as films deposited on electrodes, and in the solid state via iodine doping. Solution cyclic voltammetric oxidation and reduction has shown that the polymer, where R/R is Me/Me, reversibly oxidizes in methylene chloride in two stages, apparently with the first oxidation being on alternating iron atoms along the chain.29 Films cast on electrodes behave in a similar way and also show an electrochromic response to oxidation and reduction.30... 

Figure 4.8-5 Raman spectra of poly(acetylene), degraded by exposure to ambient conditions. The numbers refer to the exposure time in hours, according to Knoll and Kuzmany, 1984 (a), and to the conductivity of the samples after iodine doping with different concentrations of defects, characterized by the ratio R of the satellite peak intensity to the primary- peak intensity of the C=C stretching mode, according to Schaefer-Siebert et al. 1987 (b).

As mentioned in the introduction, the electrical conductivity upon doping is one of the most important physical properties of conjugated polymers. The conductivity ranges from lOOOOOS/cm for iodine-doped polyacetylene [41], 1000 S/cm for doped and stretched polypyrrole [42], to 500 S/cm for doped PPP [43], 150 S/cm for hydrochloric acid doped and stretched polyaniline [44], and 100 S/cm for sulfuric acid doped PPV [45] to 50 S/cm for iodine-doped poly thiophene [46]. The above listed conductivities refer to the unsubstituted polymers other substitution patterns can lead to different film morphologies and thus to a different electrical conductivity for the same class of conjugated polymer in the doped state. 

Despite their inherent electronic advantages, CT complexes and radical cation salts tend to be brittle and unprocessable. This problem might be overcome by the incorporation of oligomeric tetrathiafulvalenes in polymers, whereby the TTFs can be part of a main-chain or side-chain polymer. The key concern thereby is to achieve the suitable packing of the donor moieties, which is, of course, less perfect than in the crystalline state. Remarkably, the rigid-rod poly-TTF 164 could be made recently by a precursor route in which 164 is made by dimethyl disulfide extrusion of the precursor polymer (scheme 39). The electrical conductivity after iodine doping amounts to 0.6 S/cm [221]. Other examples of TTF-containing polymers, either in the backbone [222] or in the side-chain [223], are summarized in chart 25. 

Figure 4 Overview of conductivity of conducting polymers at room temperature, (a) stretched [CHClj)], (from Ref. 43a), (b) stretched [CHCIj)] (from Ref. 43b), (c) [CH(l3)], (from Ref. 43c), (d) [CH(l3)], (from Ref. 43d), (d ) [CH(1,)], (from Ref. 43e), (e) stretched PAN-HCl (from 43f), (f) PAN-CSA from m-cresol (from Ref. 43g), (g) PAN-CSA from OT-cresol (from Ref. 43h), (h) PAN derivative poly(o-toluidine) POT-CSA fiber from m-cresol (from Ref. 43i), (i) POT-HCl (from Ref. 43j), (j) sulfonated PAN (from Ref. 43k), (k) stretched PPy(PFg) from (Ref. 431), (1) PPy(PF ) ( ) PPy(TsO) (from Ref. 43m, 43n), (m) iodine doped poly(dodecylthiophene) (from Ref. 43o), (n) FeCl4 doped PT (from Ref. 43p), (o) PPV(H2S04) (from Ref. 43q), (p) PPP(Asp5) (from Ref. 43r), (q) Kr- implanted (polyphenylenebenzobisoxazole) (from Ref. 43s), (r) undoped trans-(CH (from Ref. 43t), (s) undoped cA-(CH)x from (Ref. 43u), (t) undoped PAN (EB) (from Ref. 43v), (u) undoped PPy (from Ref. 43w), (v) undoped PT (from Ref. 43p, (w) undoped PPV (from Ref. 43x), (x) undoped PPP (from Ref 43y). The conductivity reported for the undoped polymers should be considered an upper limit due to the possibility of impurities.

Poly(arylenevinylene)s based on naphthalene (JJ7) and thiophene (118, 119) have been reported. When naphthalene was substituted for benzene in the polymer structure, the resulting conductivity for the AsFs-oxidized polymer was 10 S/cm. Orientation of the polymer via stretch alignment has not been reported. The thiophene derivative, however, was stretch aligned (118) and doped with iodine and FeCl3. Conductivities of2700 were obtained with iodine-doped samples having elongation ratios of 6. The anisotropy of the conductivity was 35. 

Enzymatically synthesized polyphenol derivatives are expected to have great potential for electronic applications. The surface resistivity of poly(p-phe-nylphenol) doped with nitrosylhexafluorophosphate was around 105 Q.4a The iodine-labeled poly(catechol) showed low electrical conductivity in the range from 10 6 to 10 9 S/cm.48 The iodine-doped thin film of poly (phenol- co- tetradecyloxyphenol) showed a conductivity of 10 2 S/cm, which was much larger than that obtained in aqueous 1,4-dioxane.24a The third-order optical nonlinearity (%3) of this film was 10 9 esu. An order of magnitude increase in the third-order nonlinear optical properties was observed in comparison with that prepared in the aqueous organic solution. 

Poly(ferrocenylene vinylene) derivatives 68 with values of 3,000-10,000 and polydispersities of ca. 2.2-2.8 (determined by GPG) were synthesized in 1995 in high yields via a titanium-induced McMurry coupling reaction of the corresponding alkylferrocenyl carbaldehyde monomers (Equation (26)). " Gharacterization of these soluble polymers by NMR and IR revealed the presence of trans-Yinylcnc units. The UV-VIS spectra of the polymers are similar to those of the monomers and this indicates a fairly localized electronic structure in the former. The relatively limited electron localization is also reflected in the electrical and optical properties. For example, the values for iodine-doped conductivity a= 10 Scm ) and non-linear third-order optical susceptibility (x = 1-4 x 10 esu) are lower than those of linear conjugated polymers such as poly(l,4-phenylene-vinylene) (a = 2.5x 10 Scm" = 8 X 10 esu). 

The synthesis of poly(ferrocenylene-vinylene) via ROMP of the vinylene-bridged [2]ferrocenophane 109 was reported in 1997 263 monomer was obtained from the McMurry coupling of l,l -ferrocenedicarbaldehyde. In the presence of a molybdenum ROMP catalyst, 109 was found to undergo polymerization (Scheme 11) to give an insoluble orange powder 110, which exhibited a conductivity of 10 S cm after iodine doping. Partially soluble block co-polymers 111 were also... 

In 5 h, the polymer pellet exhibited a maximum in the conductivity and then began to decrease slowly. When film-type polymer was exposed to iodine vapor, it changed from dark violet to blue-black and the electrical conductivity increased from 10 ° Q cm to 10 Q cm . The maximum electrical conductivity of iodine-doped poly(DPDPM) is smaller than that of iodine-doped poly(l,6-heptadiyne), which is reported to have a value of 10 —10 2 Q cm . ° The activation energy for conduction was derived from the temperature, T, dependence of conductivity. For the undoped poly(DPDPM), the activation energies have... 

M. Kyotani, S. Matsushita, T. Nagai, Y. Matsui, M. Shimomura, A. Kaito, and K. Akagi, Helical carbon and graphitic films were prepared from iodine-doped helical Poly(acetylene)... 

The iodine-doped, unoriented poly(3-dodecyl thiophene)s exhibit an average conductivity of 600 S cm" and a maximum conductivity of 1000 S cm"... 

Winokur, M.J., P. Wamsley, J. Moulton, P. Smith, and A.J. Heeger. 1991. Structural evolution in iodine-doped poly(3-alkylthiophenes). Macromolecules 24 (13) 3812-3815. 

Tashiro, K., Y. Minagawa, K. Kobayashi, S. Morita, T. Kawai, and K. Yoshino. 1992. Crystal structure change of poly(3-alkylthiophene) induced by iodine doping. Polym Prepr Jpn 41 4595. 

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