Plastics polyaniline

Among conductive plastics, polyaniline has attracted much interest because of its environmental stability and its tunable electrical properties. Composite materials consisting of polyaniline nanofibers... 

Svetiidc, V. Schmidt, A. J. Miller, L. L., Conductometric sensors based on the hypersensitive response of plasticized polyaniline films to organic vapors, Chem. Mater. 1998,10,3305-3307... 

Fedorko, P., Fraysse, J., Dufresne, A., Planes, J., Travers, J.P., Olinga, T., Kramer, C., Rannou, P., Pron, A., 2001. New counterion-plasticized polyaniline with improved mechanical and thermal properties comparison with PANI-CSA. Synthetic Metals 119, 445-446. 

G. Gustafsson, G.M. Treacy, Y. Cao, F. Klavetter, N. Colaneri, and A.J. Heeger, The plastic LED a flexible light-emitting device using a polyaniline transparent electrode, Synth. Met., 57 4123-4127, 1993. 

Solid-contact pH sensors can be constructed by using polypyrrole [45,59] or polyaniline [92,96] as ion-to-electron transducer in combination with pH-selective membranes based on plasticized PVC [45,59,92,96]. The dynamic pH range of the sensors depend on the pH ionophore used in the plasticized PVC membranes, as follows tri-n-dodecylamine (pH 2-12) [45], tris(2-phenylethyl)amine (pH 4.5-12.6) [59], tris(3-phenylpropyl)amine (pH 4.6-13.2) [59], tribenzylamine (pH 2.5-11.2) [92,96], dibenzylnaphtalenemethylamine (pH 0.65-10.0) [96], dibenzylpyrenemethyl-amine (pH 0.50-10.2) [96]. Suggested applications include pH measurements in body fluids such as serum [45,96], whole blood [92], and cow milk [59]. 

Solid-state sensors for anionic surfactants can be constructed by using polyaniline as sensing membrane [107,108], and by using polypyrrole as ion-to-electron transducer in combination with plasticized PYC as sensing membranes [53,66]. The sensors may be applied for the determination of dodecylsulfate in, e.g., mouth-washing solution and tap water [107], and for the determination of dodecylbenzenesulfonate in detergents [66,108]. Solid-state surfactant sensors allow a sample rate of 30 samples/h, when applied in flow-injection analysis [53]. 

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). 

Fig. VII-1 shows a schematic of the structure of a polymer LED and a picture of a thin film flexible polymer LED seven-segment display. The bottom electrode of this display was made by spin-cas ting a layer of metallic polyaniline onto a flexible plastic substrate [69]. Polyaniline was chosen as the electrode material because it is flexible, conducts current, and is transparent to visible light. The emissive layer of the display was fo med by spin casting a layer of MEH-PPV over the polyaniline. The top electrodes were formed by evaporating calcium through a patterned shadow mask. Since the conductivity of undoped emissive polymers is relatively low, it was not necessary to pattern the polymer or the bottom electrode to prevent current spreading between neighboring pixels.

A major goal of the research on conducting polymers has been the development of a rechargeable plastic battery. Cells based on polypyrrole and lithium electrodes have been developed in which the energy per unit mass and discharge characteristics are comparable to nickel-cadmium cells. Current interest appears to center around stable, processable polymers, such as polythiophene and its derivatives, and polyaniline. 

The basic structure of a typical dc-biased bilayer OLED is shown in Figure 1.5. The first layer above the glass substrate is a transparent conducting anode, typically indium tin oxide (ITO). Flexible OLEDs, in which the anode is made of a transparent conducting organic compound, e.g., doped polyaniline (see Fig. 1.2),44 or poly(3,4-ethylene dioxy-2,4-thiophene) (PEDOT)-polystyrene sulfonate (PEDOT-PSS) (see Fig. 1,2)45 deposited on a suitable plastic, e.g., transparency plastic, have also been reported. 

Fig. 4.1 shows a schematic of the structure of a polymer LED. A photo of a thin-film flexible seven-segment display fabricated from a semiconducting polymer is shown in Fig. 4.2. The bottom electrode (the anode) of this flexible display was made by spin-casting a layer of metallic polyaniline onto a flexible plastic substrate [12].

Its surface tension, furthermore, makes possible a totally unexpected technology membranes for separating gases. However, work of this kind with doped polyaniline by American scientists has not yet been taken up by industrial laboratories. We suspect that the results are not due, as claimed by the researchers, to more targeted creation of pores, but to the change in gas adsorption as a result of the modified surface tension of the doped plastic. 

Polyaniline s metallic character, its position just below silver towards the noble-metal end of the electromotive force series, and its redox behaviour mentioned above, also make it possible to use a polyaniline coating to protect metals against corrosion. Our investigations show that the plastic removes electrons from the metal and is thereby reduced, while iron, for example, is oxidised to Fe203, This oxide layer is not rust (which consists of a loose mixture of various oxides and hydroxides), but functions as a protective passivating layer, in other words prevents further... 

A battery cell where both the electrodes consist of dopable polymer is shown in Figure 5.23. The electrolyte in this case consists of Li+ClO 4 dissolved in an inert organic solvent, usually tetrahydro-furan or propylene carbonate. When two sheets of polyacetylene or PPP are separated by an insulating film of polycarbonate saturated in an electrolyte (lithium perchlorate), and completely encapsulated in a plastic casing, a plastic battery can be made. The two sheets of polyacetylene or PPP act as both anode and cathode for the battery. A schematic is shown in Figure 5.24. Although doped polyacetylene and polyaniline electrodes have been developed, polypyrrole-salt films are the most promising for practical appKcation. 

C. Zhao, S. Xing, Y. Yu, W. Zhang, and C. Wang, A novel all-plastic diode based upon pure polyaniline material, Microelectron.. J., 38, 316-320 (2007). 

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