Ionically conducting polymers

This article addresses the synthesis, properties, and appHcations of redox dopable electronically conducting polymers and presents an overview of the field, drawing on specific examples to illustrate general concepts. There have been a number of excellent review articles (1—13). Metal particle-filled polymers, where electrical conductivity is the result of percolation of conducting filler particles in an insulating matrix (14) and ionically conducting polymers, where charge-transport is the result of the motion of ions and is thus a problem of mass transport (15), are not discussed. 

An example of an ionically conductive polymer is polyethylene oxide containing LiC104, which is used as a solid phase electrolyte in batteries. 

A completely separate family of conducting polymers is based on ionic conduction polymers of this kind (Section 11.3.1.2) are used to make solid electrolyte membranes for advanced batteries and some kinds of fuel cell. 

The active layer consists of a polymer having electronic conductive, ionic conductive, and luminescent properties, is blended with an ionic salt [48]. The polymer with the required properties can be realized by a blend of a conjugated and an ionic conductive polymer [481 or by specially designed polymers [71-73],... 

For this reason, other types of electrolytes are used in addition to aqueous solutions (i.e., nonaqueous solutions of salts (Section 8.1), salt melts (Section 8.2), and a variety of solid electrolytes (Section 8.3). More recently, a new type of solid electrolyte is being employed more often (i.e., water-impregnated ionically conducting polymer films more about them in Chapter 26). 

In this chapter we focus on two electrochemically relevant, active polymer types ionically conductive polymers and electronically conductive polymers, and discuss new developments emerging in their context. 

In battery applications, new hthium ion batteries called lithium ion polymer batteries (or more simply but misleadingly, lithium polymer batteries) work with a full matrix of ionically conducting polymer, this polymer being present inside the porous electrodes and as a separator between the electrodes. They are offered in attractive flat shapes for mobile applications (mobile phones, notebooks). 

Ion exclusion chromatography, of ascorbic acid, 25 760 Ion hopping, 14 469 Ionic aggregates, 14 463—466 Ionically conducting polymers, 13 540 Ionic carbides, 4 647 Ionic compounds, rubidium, 21 822 Ionic conduction, ceramics, 5 587-589 Ionic crystals, 19 185. See also Silver halide crystals... 

A number of important issues involving the structure and dynamics of ionically conducting polymers have yet to receive thorough theoretical consideration. For example, in the case df multivalent cations, some systems exhibit cation transport whereas others do not, due to strong cation solvation. Therefore a term associated with ion-polymer dissociation must be important in systems which are on the borderline between these two extremes. This term is likely to be of the form ikHi, /2RT). 

It usually takes place close to the melting temperature of the polymer when the pores collapse turning the porous ionically conductive polymer film into a nonporous insulating layer between the electrodes. At this temperature there is a significant increase in cell impedance and passage of current through the cell is restricted. This prevents further electrochemical activity in the cell, thereby shutting the cell down before an explosion can occur. 

An alternative to ion-blocking layers is to use hydrophobic ionically conductive polymers. A wide variety of polymers have been studied, however, they... 

This book focuses on three types of nonaqueous systems—liquid electrolyte solutions, ionically conducting polymers, and molten salts—with emphasis on the more commonly used liquid systems. It provides a review of a variety... 

Ionically conducting polymers and their relevance to lithium batteries were mentioned in a previous section. However, there are several developments which contain both ionically conducting materials and other supporting agents which improve both the bulk conductivity of these materials and the properties of the anode (Li)/electrolyte interface in terms of resistivity, passivity, reversibility, and corrosion protection. A typical example is a composite electrolyte system comprised of polyethylene oxide, lithium salt, and A1203 particles dispersed in the polymeric matrices, as demonstrated by Peled et al. [182], By adding alumina particles, a new conduction mechanism is available, which involved surface conductivity of ions on and among the particles. This enhances considerably the overall conductivity of the composite electrolyte system. There are also a number of other reports that demonstrate the potential of these solid electrolyte systems [183],... 

Other nonaqueous systems, which were mentioned in the first chapter, such as ionically conducting polymers, molten salts and solid electrolytes, have uses that are more specific. Hence, experimental aspects that are related to polymer based systems and molten salts are mentioned in the chapters that deal with them. 

Ionic Conducting Polymers for Applications in Batteries and Capacitors... 

Recent application of conducting polymers for electrochemical capacitors has been reviewed. The ionically conducting polymers have the potential to replace wet-type capacitors by dry-type ones. Especially important are the gel electrolyte systems whose ionic conductivity is high, and thus high capacitance can be obtained with them in EDLC. We believe that the combination of high surface area... 

The formation of the p-i-n junction is not an instantaneous process but depends on the mobility of the ions in the three-component blend consisting of an electron conductive and light-emitting polymer, an ionic conductive polymer, and an ionic salt. Therefore, the response times of conventional LECs typically are longer than those of polymer LEDs. However, if the motion of the ions can be suppressed after the junction has been formed, the response of the LECs can be drastically increased and it, therefore, should be possible to obtain fast response times similar to LEDs. 

A review of micro-electromechanical systems (MEMS)-based delivery systems provides more detailed information of present and future possibilities (52). This covers both micropumps [electrostatic, piezoelectric, thermopneumatic, shape memory alloy bimetallic, and ionic conductive polymer films (ICPF)] and nonmechanical micropumps [magnetohydrodynamic (MHD), electrohydrodynamic (EHD), electroosmotic (EO), chemical, osmotic-type, capillary-type, and bubble-type systems]. The biocompatibility of materials for MEMS fabrication is also covered. The range of technologies available is very large and bodes well for the future. 

Rhodamine 6G in an ionically conducting polymer were formed as a result of the local decomposition of the quencher, methyl viologen. The latter was incorporated inside the film with the dye and quenched the fluorescence of the Rhodamine 6G. However, when a tungsten tip biased at -4 V versus the platinum substrate was scanned at 1 /xm- s the quencher was decomposed, probably due to its reaction with hydroxyl ions that were generated at the tip, and the fluorescence of the dye was recovered. The authors concluded that the factors governing the resolution of the patterns were the... 

These cationic and anionic exchange polymers require that the mobile ions be well solvated with a polar solvent such as water. For applications such as the electrolyte phase in lithium batteries, an ionic conducting polymer is needed in which ionic mobility is obtained without the ions being solvated by water or some other solvent. This has been... 

Electrocatalytic reactions on chemically modified surfaces as well as on ionic-conducting polymer matrices are attractive new approaches and are being studied in various academic and industrial laboratories. Further work with such approaches is needed. 

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