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Emeraldine PANI

Table 19.5 Wave numbers (cm FWHM (cm ) in parentheses) and relative intensities from the Raman spectra for blend cast film containing 20% of emeraldine PANI in NR and blend cast films containing 20% of emeraldine PANI in NR de-doped by NH4OH or doped either by HCl or by corona discharge. Table 19.5 Wave numbers (cm FWHM (cm ) in parentheses) and relative intensities from the Raman spectra for blend cast film containing 20% of emeraldine PANI in NR and blend cast films containing 20% of emeraldine PANI in NR de-doped by NH4OH or doped either by HCl or by corona discharge.
Spectroelectrochemistry. The full electrochromic properties of the PANI LBL assembled films were examined using spectroelectrochemistry, taking a UV-Vis snapshot of each film at equilibrated potentials between -0.6 and 0.2 V, with results shown in Figiu 5. At very cathodic potentials, leucoemeraldine PANI exhibits a single absorbance maximum at 340 nm, with essentially no additional absorbance in the visible region. At more anodic potentials, emeraldine PANI evinces a 700 nm peak, with broad visible absorbance. [Pg.27]

In this paper we would like to propose also an additional concept of utilization of rechargeable metal-air battery with PANI/ TEG catalysts. It is necessary to note the ability of PANI based electrode to self-charge in the presence of oxygen. A deep discharge of PANI electrode leads to the transformation of emeraldine (EM) to lecoemeraldine (LEM). It is well known that LEM is chemically non-stable at the presence of oxygen due to occurance of the following reaction ... [Pg.120]

For example, the investigations of the current-generating mechanism for the polyaniline (PANI) electrode have shown that at least within the main range of potential AEn the "capacitor" model of ion electrosorption/ desorption in well conducting emeraldine salt phase is more preferable. Nevertheless, the possibilities of redox processes at the limits and beyond this range of potentials AEn should be taken into account. At the same time, these processes can lead to the fast formation of thin insulation passive layers of new poorly conducting phases (leucoemeraldine salt, leucoemeraldine base, etc.) near the current collector (Figure 7). The formation of such phases even in small amounts rapidly inhibits and discontinues the electrochemical process. [Pg.319]

Zengin et al. [41] characterized a polyaniline (PANI)/MWNT composite. The FTIR spectra of the composite film show benzoid and quinoid ring vibrations at 1500cm-1 and 1600 cm-1, respectively, which indicate the presence of emeraldine salt (ES) of polyaniline. A weak broad band near 3400 cm-1 is assigned to the N—H stretching mode. The strong band at 1150cm-1 is characteristic of PANI conductivity. The FTIR spectrum of PANI/MWNT composite in the ES form exhibits several clear differences from the spectrum of neat ES PANI (1) the composite spectrum shows an inverse... [Pg.515]

PANI is usually produced by the anodic oxidation of aniline in acidic aqueous solution [5, 139], but can also be produced by chemical oxidation [138b, 140]. Hence, it is not surprising that the oxidation of PANI is pH-dependent and that, therefore, in addition to electron-transfer processes, proton-transfer reactions occur during charging. Although it is usually assumed that PANI has a chain structure (emeraldine) with head-tail connections... [Pg.635]

PANI is unique in that its most oxidized state, the pernigraniline form (which can be accessed reversibly), is not conducting. In fact, it is the intermediately oxidized emeraldine base that exhibits the highest electrical conductivity. Protonic Acid Doping is the most general means by which to obtain this partially pro-tonated form of PANI [301]. Exposure of the emeraldine salt to alkali solutions reverses this process and brings a return to the insulating state. [Pg.107]

Results and Discussion. The 2-ethyl polyaniline concentration in the silica gel film was determined by constructing a Beer s law calibration curve from solutions of known concentration. Assuming an average molecular weight of 5000, the 2-Et PANi concentration in the silica gel was found to be 9.6 x 10 4 M. The refractive indices of CS2 and 2-Et PANi SiC>2 were estimated to be 1.6 and 1.4 at 1.06 im, respectively. The emeraldine base doped silica gel was found to have low losses due to scatter, and exhibited good transparency at 1.06 im. Spectrophotometric measurements at 1.06 fim yielded absorption coefficients of 0.1 cm-1 (> 99% T over 1 mm pathlength) for the CS2 reference and 4 cm 1 (96% T over 1 mm pathlength) for the 2-Et PANi doped silica film. [Pg.549]

Since the acid-base (precipitation) reaction takes place in non-aque-ous solution (isopropanol), a glass pH electrode could not be used to follow the titration. However, PANI is known to be pH sensitive as a result of the acid-base equilibrium between the emeraldine base (EB) and emeraldine salt (ES) forms of PANI [1-3]. Interestingly, the GC/ PANI electrode was found to give a reproducible response during the titrations despite the presence of the precipitate (trimeprazine tartrate) in the stirred solution. The same GC/PANI electrodes were used repeatedly for more than 2 months without any significant changes in the... [Pg.1000]

Scheme 1 Doping of PANI in its emeraldine base form with CSA... Scheme 1 Doping of PANI in its emeraldine base form with CSA...
In the undoped state, PAni is a base. Three molecular structures are possible, one of them being the so-called emeraldine base (EB) shown in Fig. 1 of Chapter 11 [52]. There are several differences between it and the other CP chains discussed above Due to the presence of the N atoms, the chain has a zigzag shape and the benzene rings have either a benzene-like or a quinone-like bond pattern (see Chapter 11, Section IV.B.l) and may be twisted. In principle, the number of independent structural parameters is even larger than for the other CPs. However, quite a good (albeit partial) understanding of the structure has been achieved, as shown in Ref. 24, for instance. [Pg.552]

PAni has a very complex structure and doping behaviour, see Fig. 9.6, and the spectra are sensitive to the polymer morphology, the level of oxidation and degree of protonation. This accounts for the considerable variation in tire spectra that have appeared in the literature. The effects are illustrated in Fig. 9.33 for various forms of the protonated salt. These spectra refer to dried films, electrochemically prepared at different electrode potentials, and subject to oxidation by exposure to air. This variation in preparation conditions means that the degrees of oxidation and protonation are not well defined, as evidenced by the pronounced differences in the spectra of the emeraldine prepared at the... [Pg.383]

Unsaturated heterocycles and aniline have been polymerized either chemically or electrochemically on electrode surfaces. The systems are attractive as they are often significantly more stable than PA under atmospheric conditions. The importance of quinoid vs. aromatic structure becomes apparent if the chemistry and conductivity of polyaniline fPANIl is examined. The initial emeraldine salt product of PANI is believed to have the following... [Pg.303]

FIGURE 1.2. Molecular structure of widely used it-conjugated and other polymers (a) poly(para-phenylene vinylene) (PPV) (b) a (solid line along backbone) and it ( clouds above and below the a line) electron probability densities in PPV (c) poly(2-methoxy-5-(2 -ethyl)-hexoxy-l,4-phenylene vinylene) (MEH-PPV) (d) polyaniline (PANI) (d.l) leucoemeraldine base (LEB), (d.2) emeraldine base (EB), (d.3) pernigraniline base (PNB) (e) poly(3,4-ethylene dioxy-2,4-thiophene)-polystyrene sulfonate (PEDOT-PSS) (f) poly(IV-vinyl carbazole) (PVK) (g) poly(methyl methacrylate) (PMMA) (h) methyl-bridged ladder-type poly(jf-phenylene) (m-LPPP) (i) poly(3-alkyl thiophenes) (P3ATs) (j) polyfluorenes (PFOs) (k) diphenyl-substituted frares -polyacetylenes (f-(CH)x) or poly (diphenyl acetylene) (PDPA). [Pg.4]


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See also in sourсe #XX -- [ Pg.66 ]




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