Polyaniline Organic dispersions

In most aqueous and organic systems, polyaniline is dispersed in the water phase since protonated polyaniUne in the emeraldine salt form is hydrophilic. However, there are exceptions, e.g., when the... 

In conclusion, we have demonstrated a facile route to obtain processable organic dispersions of polyaniline with and without SWNT. The dispersions are studied with... 

Transition metal compounds, such as organic macrocycles, are known to be good electrocatalysts for oxygen reduction. Furthermore, they are inactive for alcohol oxidation. Different phthalocyanines and porphyrins of iron and cobalt were thus dispersed in an electron-conducting polymer (polyaniline, polypyrrole) acting as a conducting matrix, either in the form of a tetrasulfonated counter anion or linked to... 

Polypyrrole/poly(ethylene-co-vinyl acetate) conducting composites with improved mechanical properties were prepared by a similar method [167], In addition, polyaniline/polystyrene [168] and polyaniline/poly(alkyl methacrylate) [169] composites have been synthesised. A solution of persulphate in aqueous HC1 was added to an o/w HIPE of polymer and aniline in an organic solvent, dispersed in aqueous SDS solution, causing aniline polymerisation. Films were processed by hot- or cold-pressing. 

In an attempt to overcome the low infusible character and low solubility of aniline, dispersion polymerization of aniline was conducted in water-dispersible colloidal particles that can be cast as films or blended with other materials to prepare composites. HRP mediated polymerization of aniline in a mixture of phosphate buffer and organic solvent resulted in polyaniline composed of ortho-directed units and para-directed units. Increasing the pH or adopting an organic solvent with a high dielectric constant, enhanced the production of ortho-directed units [54]. These ortho-directed polyanilines were more thermally flexible and electrically conductive. 

A characteristic feature of the parent polypyrroles, polythiophenes and polyanilines is their insolubility in water and common organic solvents (although the EB form of polyaniline is soluble in NMP, DMSO and several other solvents). This intractability and consequent difficulties in processing have until recently limited their exploitation. However, the introduction of substituents onto the aromatic rings of the polymers, the use of surfactant-like dopant anions and the generation of colloidal dispersions have markedly enhanced the processability of ICPs (see Section 8 below). 

Very few CPs are produced in bulk quantities. Polyphenylene sulfide, a member of the third generation of polymers, was produced in bulk quantities many years before CPs were established and its dopability was elucidated. Polyethylenedioxythiophene is commercially available as a water-based colloidal dispersion (Baytron P water dispersion), and presumably as dispersible powders. The powders with a conductivity of 5-10 S/cm can be dispersed in thermoplastic polymers and in organic solvents such as xylene. Polyaniline doped with dodecylbenzene sulfonic acid and complexed with zinc dodecylbenzene sulfonate is commercially available as a powder, which can be dispersed in polyolefins. The same polymer doped with p-toluenesulfonic acid is also available as a dispersible powder, Ormecon, and in a predispersed form for solution processing in polar and nonpolar media. Based on Ormecon PANi, there are many commercial products marketed for many different applications. 

Fig. 3.10. Some of the more commonly encountered organic conductor materials (a) polypyrrole, (b) polyaniline, and (c) poly(3,4-ethylenedioxythiophene) (PEDOT). When combined with water soluble organic acids (e.g. sulfonic acids like benzosul-fonic acid) many of these polymers can form doped complexes which are highly conductive and can be dispersed into suspension. Substituted versions of these polymers which are self-doped have also been developed.

It was not until 1984 and 1985 that we succeeded in comminuting polypyrrol and polyaniline in the melt by means of ultrasound and dispersing them in special polymer blends. Only two years later we were able to report to the world conference on Organic Metals in Kyoto (Japan) that dispersed conductive polymers displayed a conductivity breakthrough at a concentration of less than ten percent by volume in a thermoplastic polymer matrix—for example a polyvinylchloride (PVC), polyester or polyurethane—and could be processed in the form of such blends. 

Thus when dispersing polyaniline we found a different diameter for the resulting particles in low-molecular media—for example 10 nanometres in organic solvents—than in high-polymer systems (up... 

Dispersions of polyaniline in isopropanol-based organic solvents were investigated by photon correlation spectroscopy experiments and the results of these experiments are shown for neutral PAni in Figure 11,41 and for doped PAni in Figure 11,42, Therefore it is important to note that the dispersions used (0,1% concentration) are completely clear and have been filtered through 1 pm filters or pressure filtered through membrane filters [84],... 

B. Wessling and J. Posdorfer, Nanostructures of the dispersed organic metal polyaniline responsible for macroscopic effects in corrosion protection, Synth. Met., 102, 1400-1401 (1999). 

FIGURE 1.5 Laser Doppler measurement of polyaniline primary particles in an organic solvent dispersion. (Reprinted from Wessling, B., Handbook of Nanostructured Materials and Nanotechnology, vol. 5, ed. H.S. Nahva, Academic Press, New York, 1999, 525. With permission, copyright 2000 Elsevier Science)... 

FIGURE 1.13 Transformation of a pure premetallic organic metal (100% PAni) to a truly metallic polyaniline in blends after dispersions. (Reprinted from Gospodinova, N., Mokreva, R, Tsanov, T., and Terlemeyzan, L., Polymer, 38, 743, 1997. With permission. Copyright 1996 Elsevier Science)... 

From the beginning of their history in the late 1970s, conductive polymers (organic metals) have been considered as intractable and insoluble. It was an important goal in basic research as in application-oriented materials science to develop techniques by which they could be processed. The use of solvents was one of the options. As early as 1983-84, after five years of research, we happened to create the first clear dispersions of polyacetylene, polypyrrole, and polyaniline [42], with and without the presence of conventional polymeric binders. This was the beginning of nanotechnology with organic metals. 

Since 1986, there has been no International Conference on Science and Technology of Synthetic Metals in which the question—solution or dispersion —did not raise exciting discussions. Most of the scientists support the position [43] that clear (colored) mixtures of (organic) solvents with intrinsically conductive polymers (OM) are solutions. (The first reports of soluble and moldable conducting polymers were published by Elsenbaumer et al. [44a,b].) Only a few support our position [42b], which considers the mixtures to be dispersions. In the recent years, the debate concerning polyaniline and solvent systems has attracted growing interest. 

The copper substrate was a sputter-cleaned pure copper foil. On exposure of the copper foil to air, polyaniline was deposited onto it using a commercially produced polyaniline dispersion in an organic solvent (Ormecon GmbH). The sample was kept in air at room temperature and after a certain time in air was transferred back into the main chamber for analysis. XPS measurements were performed using... 

A polyanrline-poly(butyl acrylate-vinyl acetate) composite exhibiting electroactivity and having a conductivity of 2.2 S/cm was prepared by emulsion polymerization. The composite was soluble in common organic solvents and a stable water-based dispersion could also be prepared. Films cast from aqueous media had exceptional mechanical properties and had excellent adhesion to steel [144]. From the same group, a polyaniline and polyvinyl alcohol electroactive composite has been synthesized by... 

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