Plastics polypyrrole

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). 

Concentration of antistats in plastics is mostly 0.1 to 2 %. Special grades of electroconducting (EC) carbon black are used in PO at levels higher than 10 % (Accorsi and Yu, 1998). Other conducting fillers incorporating antistatic effects, such as metals or organic semiconductors (e.g. polypyrrole) are not commonly used in plastics for contact with food. 

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 chemical synthesis of Polypyrrole-themio-plastic powder blend [127]. 

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. 

High quality thin films of doped polypyrrole and doped polyaniline can be conveniently deposited during a few minutes at room temperature on glass and plastic substrates from dilute aqueous solutions of the respective monomer as it undergoes oxidative polymerization (5-5,75). We find that the deposition rate and the properties of the films are greatly dependent on the nature of the substrate surface, e.g., whether deposited on hydrophilic or hydrophobic surfaces. 

Figure 9. Relationship between transparency (% transmittance in air at 600 nm) and applied voltage of polymer chspers liquid crystal display devices constructed using two ITO glass electrodes and two polypyrrole film (on plastic) electrodes as the conducting transparent substrates.

M-N4 complexes have also been used to modify electrodes by incorporation into other polymers" " , such as plasticized poly(vinyl chloride) and polypyrrole. 

Fig. 7.24 A schematic drawing of an electrochemical triple-layer actuator (polypyr-role C104 nonconducting, double-sided plastic tape polypyrrole) immersed in aqueous LiC104 solution, and the macroscopic movement of the actuator produced due to a volume change in the PP films. (Reproduced from [285] with the permission of Elsevier Ltd.)...

The most studied systems have been polypyrrole/ PVC blends [372-5]. The electrochemical polymerization of pyrrole on a platinum electrode covered with a film of PVC produces a dark-brown, ductile and flexible composite polymer film with an electrical conductivity comparable to polypyrrole (5-50 S cm ), and mechanical properties very similar to PVC. Bargon et al. [373] have observed that the mechanical properties of these PPy/PVC blends can be further improved by the addition of poly(chloroprene) rubber as a plasticizer. 

Polypyrrole has been used in the construction of an all-plastic battery. Polyaniline has become a popular conducting polymer. 

Additives used in final products Fillers aluminum, barium sulfote, aluminum hydroxide, glass fiber, mica, montmorillonite, Ni-BaTi03, nickel, silica, titanium dioxide, titanium fiber Plasticizers di-(2-ethylhexyl) phthalate, 2-hydroxyethyl methacrylate, 4-cyanophenyl 4-heptylbenzo-ate Antistatics copper dimethacrylate, glycerol monolaureate, indium tin oxide, lauramide diethanolamide, polyaniline, polypyrrole Antiblocking crosslinked siloxane particles Release magnesium stearate, methylpolysilsiquioxane, silicon nitride, stearic add Slip emcamide, slip ... 

One of the main limitations of intrinsically conductive polymers (ICP s) towards their wide application as conductive additives for thermoplastics is their poor thermal-oxidative stability at typical melt processing temperatures (i.e., above 200 °C). On the other hand, the use of high surface area carbon blacks (CB) as conductive additives is limited due to the increased melt viscosity of their blends with thermoplastics. Eeonomers are a new class of thermally stable, chemically neutral, and electrically conductive composites made via in-situ deposition of conductive polyaniline (PANI) or polypyrrole (PPY) on CB substrates. Eeonomer composites are more stable (up to 300 °C) than pure ICP s and more easily processible with thermoplastics than CB. Use of Eeonomers as conductive additives for plastics lead to compounds with improved electrical, mechanical, and processing properties. By varying Ae conductive polymer to CB ratio, it is possible to fine tune the polarity of Eeonomer composites and achieve very low percolation thresholds. This control is possible because of preferred Monomer localization at the 2D phase boundary of the immiscible polymer blends. 

Eeonomers are a new class of conductive additives for thermoplastics made via in-situ deposition of intrinsically conductive polyaniline or polypyrrole on carbon black. Eeonomers are highly thermally stable, pH neutral conductive materials that are compatible with the chemistry and melt processing conditions of acid sensitive polymers. Compounding studies with thermoplastics indicate better electrical, mechanical, and melt flow properties of Eeonomer blends as compared to blends with traditional carbon blacks. In co-continuous plastic blends it was possible to fine tune the polarity of Eeonomer by varying the conductive polymer to CB ratio. The same variation affords very low percolation thresholds due to preferred Eeonomer localization at the 2D phase boundary. 

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