Conductivity of doped poly

FIGURE 6.3 Conductivities of doped poly acetylenes conductivities of insulators, semiconductors and metals are given for comparison. 

The conductivity of doped poly(3,4-dimethylpyrrole) is lOScm-1, while conductivities of poly(diphenylpyrrole) and of poly(A-methyl pyrrole) are both about 10 3 S cm-1, very much reduced from pyrrole and dimethylpyrrole. This is attributed by Street to non-planarity of the substituted polymers 393). 

Additional annealing of doped polymers also accelerates the process of dedoping. Li and Wan (1999) have shown that temporal change in film conductivity of doped poly aniline at room temperature is increased strongly after thermal treatment of doped polymer at 7=150 °C. Results of this research are shown in Fig. 19.6. We need to recognize that the indicated effect limits the application of any thermal treatments during gas sensor fabrication. It was noted that the conductivity of PANICS A and PANI-p-TSA are the most stable below 200 °C, while the stability of PANI films doped with H SO and H PO are much better than the PANI-HCIO and PANI-HCl after thermal treatment at a high temperature (200 °C) (Li and Wan 1999). 

Table 15.7 Conductivity of doped poly[(silylene)diethynylenes] and poly[(germylene)-...

Fig. 6-26 fa.b) (a) Dependence of Conductivity of Doped Poly(aniline) (Emer-aldine Oxidation State) on Molecular Weight. 

In 1958, Natta and co-workers polymerized acetylene for the first time by using a Ti-based catalyst. This polymerization proceeds by the insertion mechanism like the polymerization of olefins. Because of the lack of processability and stability, early studies on polyacetylenes were motivated by only theoretical and spectroscopic interests. Thereafter, the discovery of the metallic conductivity of doped polyacetylene in 1977 stimulated research into the chemistry of polyacetylene, and now poly acetylene is recognized as one of the most important conjugated polymers. Many publications are now available about the chemistry and physics of polyacetylene itself. 

The most productive group in the networks field is the group of Tomoji Kawai from Osaka that pubhshed an extended series of experiments on different networks and with various doping methods [69, 70, and references therein]. In one of their early experiments they measured the conductivity of a single bundle [67]. This was done in a similar way to the de Pablo experiment [58] (see Fig. 7), placing the bundle between a metal-covered AFM tip on one side of the molecule and under a metal electrode that covered the rest of the bundle (see Fig. 9). The conductivity of a poly(dG)-poly(dC) bundle was measured as a function of length (50-250 nm) and was compared with that of a poly(dA)-poly(dT) bundle. The results showed a very clear... 

LB films prepared from poly-thiophene-3-acetic acid stearylamine or sulfonated polyaniline stearylamine polyion complexes, transferred to substrates, and doped by SbCls Absorption and infrared spectra, X-ray diffraction, and conductivity measurements Lateral d.c. conductivities of doped films were moisture dependent and were as high as 2 S cm"molecular organization consisted of randomly oriented polymers lying as extended chains parallel between the substrates and sandwiched between layers of stearylamine molecules whose chains were interdigitated 772... 

So far, we have ignored the primary reason poly films are used in integrated circuits. Heavily-doped poly is used as a gate electrode, and the electrical conductivity of this material is of prime importance. Therefore, we have to inquire into the feasibility of doping poly as it is being deposited by CVD. 

In the past three decades, several types of r-electron systems have shown very interesting features in electrical transport properties [1-4]. Charge-transfer complexes, intercalated graphite, conjugated polymers, carbon-60, carbon nanotubes, etc., are some of the well-known r-electron systems. Polymeric materials were considered as insulators before the discovery of metallic poly(sulfur nitride), [SN],, and the enhancement of conductivity in doped poly acetylene, (CH),, by several orders of magnitude [4, 5]. 

Zotti, G., S. Zecchin, G. Schiavon, B. Vercelli, A. Berlin, and E. Dalcanale. 2003. Potential-driven conductivity of polypyrroles, poly-JV-alkylpyrroles, and polythiophenes Role of the pyrrole NH moiety in the doping-charge dependence of conductivity. Chem Mater 15 4642-4650. 

Polythiophenes in the neutral state are stable in the dark under atmospheric conditions but the conductivity of doped polythiophene and poly(3-alkylthiophene)s decreases rapidly. This lack of stability is one of the major barriers to industrial application of polythiophenes as conductive materials. Extrinsic and intrinsic factors determine the stability of a conductive polymer. Extrinsic instability is mainly due to the reaction of the charged defects with water vapor and oxygen. A... 

Electrical conductivity of the iodine-doped copolymer prepared via the first route is 10 S cm and l Scm for the copolymer prepared by the second route. The conductivity of the 10 1 (3-MT/ MMA) copolymer after iodine doping is 0.2 S cm , indicating that conductivity increases with increasing concentration of thiophene units. Quantitative data on the solubility of doped poly(3-butylthiophene) and poly(3-methylthiophene-co-3-butylthiophene) are... 

In a short communication [81], Pei and Inganas reported that these copolymers, which are electro-chemically prepared, are stable, processable and conducting. The conductivity of the doped copolymer held at 110°C in air decreases by less than one order of magnitude after 1 hour, whereas that of doped poly(3-OT) decreases by four orders of magnitude. The... 

One active area of research is completely missing. These are the optical and electrical properties, with effects such as the high conductivity of doped conjugated polymers, electro-luminescence in polymeric light emitting diodes, or the ferro- and piezoelectricity of poly(vinylidene fluoride), to cite only a few examples. There is no good reason for this omission, only that I did not want to overload the book with another topic of different character which, besides, mostly employs concepts which are known from the physics of semi-conductors and low molar mass molecules. 

Oxidative doping of PcM, e.g. with iodine, often results in highly increased conductivities of the poly crystalline samples. Undoped PcNi (j8-modifica-tion. Figure 13.15b) shows a powder conductivity of 10 S/cm, whereas PcNil (formed by iodine doping) exhibits a powder conductivity of 0.7 S/cm [102]. For many doped, especially iodinated, metal complexes the crystal structure is known. Depending upon the... 

Similar routes have been employed for poly(2,5-thiophenediylvinylene) and poly(2,5-furandiyl-vinylene) (equation Conductivities of doped films of these polymers are in the range... 

Another interesting applications area for fullerenes is based on materials that can be fabricated using fullerene-doped polymers. Polyvinylcarbazole (PVK) and other selected polymers, such as poly(paraphcnylene-vinylene) (PPV) and phenylmethylpolysilane (PMPS), doped with a mixture of Cgo and C70 have been reported to exhibit exceptionally good photoconductive properties [206, 207, 208] which may lead to the development of future polymeric photoconductive materials. Small concentrations of fullerenes (e.g., by weight) lead to charge transfer of the photo-excited electrons in the polymer to the fullerenes, thereby promoting the conduction of mobile holes in the polymer [209]. Fullerene-doped polymers also have significant potential for use in applications, such as photo-diodes, photo-voltaic devices and as photo-refractive materials. 

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