Emeraldine salt , polyaniline formation

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. 

Encapsulation chemistry similar to that described above (exchange of anilinium, followed by oxidation with peroxydisulfate) was foimd to produce polyaniline not only in zeolite Y, but also in montmorillonite clay. 5 Spectral features (UV-VIS, IR and EPR) of the products were indicative of emeraldine salt and base formation, respectively. The change in basal spacing of the montmorillonite upon intercalation provided additional evidence for the inclusion polymerization. 

A synthetic protocol for the formation of conducting filaments of polyaniline in the 3 nanometer wide channels of the aluminosilicate MCM-41 was developed (Figure 11).1°° Aniline vapor was allowed to diffuse into the dehydrated channels of the host at room temperature, followed by immersion into an aqueous solution of peroxydisulfate at 273 K. This reaction produced encapsulated polyaniline filaments. Spectroscopic evidence including UV-VIS and infrared data showed that the filaments are in the protonated emeraldine salt form (for example, Raman spectra exhibit modes indicative of the protonated quinone radical cation structure). A single, rather broad (8 G) electron spin resonance line (for an evacuated sample), at g = 2.0032 suggested slightly lower... 

The formation of electrically conductive fibers of polyaniline blended with poly(p-phenylene terephthalamide) processed from sulfuric acid was also reported by Hsu et al. [72]. A thoroughly mixed solution of 0.2 wt% emeraldine base and 17.6 wt% poly(p-phenylene terephthalamide) was dissolved in sulfuric acid and this dope solution was extruded at 80°C through a 20-hole spinneret into a 1°C water coagulation bath. The continuous 20 filament yarns that were collected on the bobbin were thoroughly washed with water, which probably led to partial deprotonation of the emeraldine salt. However, the... 

Fig. 9 a Emeraldine salt foim of graphene-polyanilines nanocomposite, b emeraldine base form of graphene-polyaniline nanocomposites, c formation of CPs wrapping around graphene [63] (Reprinted with permission from Ref. [63] Copyright (2013) by Elsevier)... 

The emeraldine base form of polyaniline may also react in non-aqueous electrolytes, such as a LiClOl -propylene carbonate solution, with the formation of the conductive emeraldine hydroperchlorate salt ... 

The formation of -aminodiphenylamine is supposed to be the key intermediate in the formation of a dark green precipitate at the electrode surface during continued electrolysis of acidic aniline solutions. This has been characterized as an oligomer of aniline, for example, as the octamer emeraldine formed by a cascade of head-to-tail condensations [38,39]. Nelson, however, explained it as a mixture of mainly quinhydrone with a small amount of benzidine salt [37]. Today the electropolymerization of aniline under strongly acidic conditions is intensively studied as an important way to form the conducting polymer polyaniline [40] (see Chapters 31 and 32). 

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