Conducting polymers operation principle

Actuators Based on Conducting Polymers Operation Principle. 239... 

Polyaniline is the conducting polymer most commonly used as an electrocatalyst and immobilizer for biomolecules [258-260]. However, for biosensor applications, a nearly neutral pH environment is required, since most biocatalysts (enzymes) operate only in neutral or slightly acidic or alkaline solutions. Therefore, it has been difficult or impossible to couple enzyme catalyzed electron transfer processes involving solution species with electron transport or electrochemical redox reactions of mostly polyaniline and its derivatives. Polyaniline is conducting and electroactive only in its protonated (proton doped) form i.e., at low pH valnes. At pH values above 3 or 4, polyaniline is insulating and electrochemically inactive. Self-doped polyaniline exhibits redox activity and electronic conductivity over an extended pH range, which greatly expands its applicability toward biosensors [209, 210, 261]. Therefore, the use of self-doped polyaniline and its derivatives could, in principle. 

At the heart of a PEM fuel cell is a polymer membrane that has some unique capabilities. It is impermeable to gases but it conducts protons (hence the name, proton exchange membrane). The membrane that acts as the electrol5q e is squeezed between the two porous, electrically conductive electrodes. These electrodes are typically made out of carbon doth or carbon fiber paper. At the interface between the porous electrode and the polymer membrane there is a layer with catalyst particles, typically platinum supported on carbon [1]. A schematic diagram of cell configuration and basic operating principles is shown in the Figure in.l. 

Since the type of electrolyte material dictates operating principles and characteristics of a fuel cell, a fuel cell is generally named after the type of electrolyte used. For example, an alkaline fuel cell (AFC) uses an alkaline solution such as potassium hydroxide (KOH) in water, an acid fuel cell such as phosphoric acid fuel cell (PAFC) uses phosphoric acid as electrolyte, a solid polymer electrolyte membrane fuel cell (PEMFC) or proton exchange membrane fuel cell uses proton-conducting solid polymer electrolyte membrane, a molten carbonate fuel cell (MCFC) uses molten lithium or potassium carbonate as electrolyte, and a solid oxide ion-conducting fuel cell (SOFC) uses ceramic electrolyte membrane. 

One notable difference of AFM in comparison with electron microscopy is the ease of sample preparation. There is no need for conductive coatings, thin sections, etc. This means that any polymer sample can in principle be analyzed by AFM, provided the part fits into the corresponding microscope. There are also stand alone AFM models that can operate on any large macroscopic surface, such as an airplane wing, to perform local analysis. 

The term reactive processing is used to describe a polymer processing that involves chemical reactions. In principle, any processing operation can be conducted as a reactive process, viz. reactive injection molding (RIM). However, most often the term refers to reactive extrusion, and in particular, to the reactive compatibilization of immiscible polymer blends, usually conducted in a TSE. During the last 50 years, the latter machines have been used as chemical reactors for the polymerization, depolymerization (chemical recycling), polymer modification and compatibilization [Brown, 1992, Xanthos, 1992 Utracki, 1989, 1991, 1994, 1997]. 

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