Water-based polyaniline

Polyaniline was used as hole injection material for polymer hght-emitting devices (PLED) spin-coated from a water-based polyaniline/poly-styrenesulfonate (PAni/PSS) dispersion. Data presented here were based on red, yellow, green, and blue LEPs. Depending on the applied bias voltages, the devices were studied by electrical impedance spectroscopy (EIS) in a wide frequency range. Experimental data could... 

With increasing environmental concerns, the development of water-based ICPs and their complex becomes a necessity. Extensive research has been conducted in this field, especially for polyaniline. Generally, water-based polyaniline can be obtained by three methods introduction of water-soluble substituent to backbone to gain water-soluble polyaniline [158, 159], emulsion polymerization to obtain water-dispersed polyaniline [160-163], and the cormterion-induced processability of doped polyaniline using a hydrophilic protonic acid [164, 165). The first two methods have a common problem of purification and efficiency. In contrast, the pure polyaniline is used in counterion-induced processability of doped polyaniline. The purification and efficiency problems do not exist with this method, so it is the most promising way to obtain water-based polyaniline. 

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. 

The commercially available, stable polyaniline dispersion for the spin coating of HILs—the developmental type Covion PAT 010—has a particle size distribution of the water-based PAT 010 compared to commercially available PEDT samples as shown in Figure 1.47. 

A water-based dispersion of polyaniline recommended for use as HIL in OLEDs (see Table 1.4). 

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... 

Electrophilic substitution is a straightforward way to functionalize polyaniline. Substitution of sulfonic acid groups on the backbone of polyaniline, as shown in Figure 2.2, was first introduced by Epstein et al. [39] in the very first report of self-doped water soluble polyaniline. Their synthetic method involved the sulfonation of polyaniline using fuming sulfuric acid. The emeraldine base form of polyaniline (0.5 g) was dissolved in 40 mL of fuming sulfuric acid with constant stirring. 

In the last few years a number of polyaniline derivatives have been developed that are soluble in the conducting form [44,46,48]. Many of these are based in organic solvents, and although some of these could in principle be used as topcoat discharge layers, water-soluble polyanilines are preferred. First of all, such polymers eliminate environmental concerns of organic solvents. Reduction of solvents is an issue of increasing importance in the electronics industry. In addition, as discussed above, water-based systems would be more compatible with current resists. 

A number of water-soluble polyaniline derivatives have been developed in recent years [39-41,49,61-65]. One method used to introduce water solubility has been to incorporate sulfonate groups onto the polymer backbone. This has been accomplished by several routes. One process involved the sulfonation of polyaniline base by treating the polymer with fuming sulfuric acid [39,62]. This results in a sulfonic acid ring-substituted derivative that is alkaline-soluble but only upon conversion to the nonconducting sulfonate salt form. A second method of introducing sulfonate groups was accomplished by de-... 

The bridging polymer is a conducting poly(3-methyIthiophene) or polyaniline and the solid state redox conduction between all electrodes is accomplished by a common coating with poly(ethyleneoxide)/Li" CF3S03- or poly(vinyl alcohol)/ The polyaniline based molecular transistor proved as a very sensitive moisture detector it works well in a dry argon atmosphere but in water saturated argon the device cuts out... 

The use of ISEs with ion-selective membranes based on plasticized PVC, as well as glass pH electrodes, is limited to the analysis of aqueous solutions. On the other hand, sensors based on conducting polymer membranes are usually insoluble in organic solvents, which extends the range of possible applications. Electrosynthesized polypyrrole doped with calcion works as a Ca2+ sensor that can be applied as indicator electrode in the titration of Ca2+ with NaF in mixed solvents, such as water-methanol (1 1) and water-ethanol (1 1) [52], Another example is the use of polyaniline as indicator electrode in order to follow the acid-base precipitation titration of trimeprazine base with tartaric acid in isopropanol solution (see Procedure 5). 

Solid-state ion sensors with conducting polymers as sensing membranes have also proved useful in some applications. Of particular importance are the pH sensors based on polyaniline that can be also applied in non-aqueous solutions. Polypyrrole-based sensors for nitrate also show great promise for water analysis. However, in addition to these two excellent examples, a large number of functionalized conducting polymers have been synthesized already, and these materials may offer unique possibilities for fabrication of durable, miniaturized ion sensors. 

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