Anion-exchange membranes, sulfonate type

Membrane Cells [198], [199]. Since 1992 Bayer has replaced the woven fabric cloth in the diaphragm cells by anion-exchange membranes of the sulfonate type. Only hydrated protons are able to pass from the anolyte to the catholyte, so that the whole cell and the electrolyte systems are simplified. Together with an optimized surface of the electrodes for better gas release, this leads to ... 

DLFCs can use a cation exchange membrane (CEM) or an anion exchange membrane as an electrolyte, the principles of which are shown in Fig. 6.1a and b. DLFCs that use acidic and alkaline reaction media correspond to the CEM and AEM types, respectively. Perfluorinated sulfonic acid membranes, that is, Nafion , are typical CEMs, in which a countercation of sulfonate can be exchanged for another... 

Membranes which may be used in the removal of alkali metal ions by electrodialysis are those which are impermeable to anions, but which allow the flow therethrough of cations. Such cation-selective membranes should, of course, possess chemical durability, high resistance to oxidation and low electrical resistance in addition to their ion-exchange properties. Homogeneous-type polymeric membranes are preferred, for example, network polymers such as phenol, phenosulfonic acid, formaldehyde condensation polymers and linear polymers such as sulfonated fluoropolymers and copolymers of styrene, vinyl pyridine and divinylbenzene. Such membranes are well known in the art and their selection for use in the method of the invention is well within the skill of the art. 

More recently, a new series of water dispersed anionic polymers, the AQ 29D, 38D and 55D polymers were released by Eastman Kodak. Since that time, these polymers were used as electrode modifier (12, 13), as covering membrane (14) and as support for enzyme immobilization (15, 16). AQ polymers are high molecular weights (14,000 to 16,000 Da) sulfonated polyester type polymers (17, 18). Their possible structures have been recently presented (18). The AQ polymer serie shows many interesting characteristics useful for the fabrication of biosensors. They are water dispersed polymers and thus compatible with enzymatic activity. They have sulfonated pendant groups similar to Nafion and they can act as a membrane barrier for anionic interferring substances and they offer the possibility to immobilize redox mediators by ion exchange. 

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