Polyaniline conventional

The emeraldine salt form of conventional polyaniline was chemically synthesized from aniline by oxidative polymerization using ammonium peroxydisulfate in an acidic media (7). Washing the salt form with 0.1 M ammonium hydroxide produces the emeraldine base form of polyaniline. Conventional polyaniline solutions were prepared in hexafiuoroisopropanol (HFIP), at a concentration of 2 mg/mL, or in A -methylpyrrolidinone (NMP), at a concentration of 1 mg/mL. 

Wnek 180> proposed that the structure of the oxidized insulating form of conventionally formed polyaniline is approximately a 50 % copolymer of diamine and diimine units, corresponding to the emeraldine structure and Hjertberg et al.180 obtained CPMAS NMR evidence for this conclusion. Some confirmation of the structure has also been obtained by chemical synthesis of the polymer182). However, Kitani et al.183) have suggested that the normal electrochemical synthesis leads to partially cross-linked polymers. 

In addition to the conventional lithographic techniques, surface patterning was performed by means of local polymerisation of the monomers under the SPM tip. These studies have been mainly focused towards electrically conductive polymers such as polypyrole, polythyophene and polyaniline. The easiest way to implement polymerisation is to set either the tip or sample potential sufficiently positive to cause the electrochemical oxidation of the monomer [438, 451 -455]. This technique enabled controlled removal and deposition of polymer dots as small as 1 nm to in a well defined pattern [453]. After deposition, the dots could be read using a conventional imaging mode (Fig. 49). 

Work with PPy and PAni has reached the industrial stage. Bridgestone-Seiko has been selling coin-shaped 3-V polyaniline-based batteries for 5 years (1987-1992), and polypyrrole-based batteries were developed by Varta/BASF in the same period. Such batteries have lower energy densities than those of conventional batteries, but they are superior in terms of selfdischarge. The main characteristics of a typical PAni battery are compared to those of lead and Cd-Ni batteries in Table 4. The values mentioned for energy density and electric capacity density refer to the active material alone. 

Table 4 Characteristics of Conventional Lead and Ni-Cd Batteries and a Typical Polyaniline Battery...

Figure 9 shows the discharge curves of a Type I polypyrrole-based, a Type II polypyrrole/poly(3-methylthiophene)-based and a Type III poly(dithieno[3,4-6 3, 4 -d]thiophene-based supercapacitor at 4 mA cm discharge current. Types I and II can be assembled using such conventional heterocyclic polymers as polypyrrole, polyaniline and polythiophene, which are efficiently p-dopable polymers and can easily be chemically or electrochemically synthesized from inexpensive... 

Another material—polyaniline in its quinoid-benzenoid-diimine form—has recently been reported to be compatible with aqueous electrolytes both in the oxidized and reduced states. As opposed to the conventional method of p-doping organic polymers by oxidative removal of electrons from the polymer 7r-system, polyaniline can be proton doped in an aqueous protic acid (HCl or HBF4) to a metallic (S — 5 cm ) iminium salt. Cells con-... 

In addition to the above-mentioned conventional polymers, several interesting developments have taken place in the preparation of nanocomposites of MMT with some specialty polymers including the N-heterocyclic polymers like poly (N-vinylcarbazole) (PNVC) [32, 33], polypyrrole (PPY) [34, 35], and polyaromatics such as polyaniline (PANI) [36-38]. PNVC is well known for its high thermal stability [39] and characteristic optoelectronic properties [40-43]. PPY and PANI are known to display electric conductivity [44-46]. Naturally, composites based on these polymers should be expected to lead to novel materials [47,48]. 

The processability of certain CEPs has been utilized in the construction of microsystems, particularly miniature sensor systems. For example, simply dip-coating connecting platinum wires with a polyaniline formulation produces a useful humidity sensor.133 CEPs can also be screen-printed or ink-jet-printed to produce the complex shapes needed for various devices. Electrodeposition of CEPs is also a popular processing method, and this technique is compatible with conventional MEMS fabrication, where lithography and etching can be used to prepattern metal electrodes. Subsequent deposition of CEP by electrochemical polymerization produces the CEP microdevice.129... 

Polyaniline (PAn) is most amenable to solution processing. The emeraldine base (EB) form of PAn is soluble in selected solvents such as methyl pyrrolidinone1 or strong acids.2 3 More recently, it has been discovered that solubility of the doped form can be induced by the use of appropriate surfactant-like molecules as dopants.4 Camphorsulfonic acid (HCSA) and dodecylbenzenesulfonic acid have proved particularly useful in this regard. Once solubilized, these PAn s can be cast into sheets or blended with other conventional polymer structures. For example, the pres-... 

This diol was mixed with other diols, then reacted with diisocyanates to form polyurethanes. The electrically conducting polymers, polyaniline and polypyrrole, prevent corrosion of steel.105 One of the best formulations uses polyaniline with zinc nitrate, which is then covered with an epoxy resin topcoat. Polyorganosiloxanes have been grafted to starch using the sol-gel method with alkoxysi-lanes. These materials have been complexed with cerium ions to provide corrosion protection for aircraft that is expected to be 50% cheaper than conventional coatings.106... 

Mecerreyes et al. [91] used ionic liquid-supported HRP in water to conduct enzyme-catalyzed free radical polymerization. In this reaction procedure, the HRP was immobilized in BMIM NTf2 by simple dissolution. This was then added to an aqueous solution of aniline, dodecylbenzenesulfonic acid (DBSA) and H202 at pH 4.3. Under these conditions, polymerization occurred immediately (as evidenced by the green color of the solution), but yield was low due to precipitation and association of polyaniline at the surface of the ionic liquid. To overcome this problem, a less hydrophobic ionic liquid, BMIM PF6 was used. In this case, the solution separated into two liquid phases after 0.5 hours one contained the polymer in water and the other was ionic liquid-immobilized HRP. The IL-HRP could be recycled and polymerization successfully repeated up to five times. The resulting polymer had similar electric conductivity properties to conventionally prepared polymer. A schematic of this process is presented in Figure 13.10. 

Textiles impregnated with conducting polymer are then associated to a bi-component epoxy based resin. It should be pointed out that the choice of compounds is crucial. Indeed, conventional hardeners containing amines will de-dope the polyaniline and subsequently induce a fall of conductivity. Due to this, a hardener made of anhydric acid should be used. 

Figure 11.59. At all tests of the DECHEMA the new polyaniline-lacquer had succeeded the requests and conventional lacquers clearly excelled. Also the tests after ASTM G-48 for gap- and hole-corrosion. The left specimen is an iron-plate coated with a polyaniline-lacquer and exhibits no rust. The right uncoated specimen exhibits rust after a short time in water [106],...

Different corrosion tests for crevice and pitting corrosion and galvanic corrosion of various pretreated (coated and uncoated) metal/steel specimens had been carried out by the DECFIEMA [120], The newly developed passivating coatings on a polyaniline basis were thereby tested for resi.stance to crevice and pitting corrosion and to galvanic corrosion and compared with conventional coating systems. In this research it was found that the first specimens supplied, displayed... 

So, there has also been considerable interest in the use of conducting polymers, particularly polypyrrole (PPy), polythiophene, and polyaniline (PANl), in the form of thin films or blends with conventional polymers as sensors for airborne volatiles such as alcohols, ethers, halogens, ammonia (NH3), NO2, and warfare simulants... 

Figure 29.5 The conventional synthesis of polyaniline and its morphology, (a, b) The oxidative polymerization reaction of aniline is typically carried out in an acidic solution (e.g., 1 M HCl) [45].

One application brings the conducting polymer as a dispersion coating to the surface [66]. A powder of polyaniline (with a particle size in the range of some tens of nanometers) is dispersed in a conventional paint, and this is painted onto the metal surface. The authors use a very low powder concentration of 4% and explain the corrosion-protection properties with a percolation model. 

P.-C. Wang, E. C. Venancio, D. M. Sarno, and A. G. MacDiarmid, Simplifying the reaction system for the preparation of polyaniline nanofibers Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media. React. Funct. Polym., 69, 217-223 (2009). 

The polyanilines,3 refer to a large class of conducting polymers which exist in three different discrete oxidation states at the molecular level, both in their doped and undoped forms. Physical mixtures of these oxidation states are also readily obtained. One of these discrete oxidation states can be doped by a non-redox process which neither adds nor removes electrons from the polymer Jt backbone. Until very recently, it was unique amongst all conducting polymers when similar effects, which have not yet been fully investigated, were discovered for some of the poly(hetrocyclicvinylenes),4. The reduced form of polyaniline can also be doped by a conventional oxidation process,. ... 

Other recent relevant developments have been the replacement of conventional acid catalysts with greener analogues. Direct esterification of carbo Q lic acids and alcohols continues to be a focus of attention. As examples, diphenylammonium triflate 8 and bulky diatylammonium sulfonates were shown to catalyse ester condensation of carboxylic acids and alcohols efficiently, and without the need for azeotropic water removal in the former case. Pentafluorophenylammonium triflate 9 was shown to be an efficient and cost-effective catalyst not only for esterification, but also for thioesterification, transesterification and macrolactone formation without requiring a dehydrating system. The superior catal)4ic efficiency of 9 relative to 8 was ascribed to the lower basicity of the pentafluoroaniline counter amine compared to diphenylamine. In related work, polyaniline... 

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