Ion-exchange Membrane Properties

Two comprehensive reviews including functional PFAVE synthesis, copolymerization of functional PFAVE with fluorooleks (mainly TFE), investigations of the structure of the copolymers as well as their ion-exchange membrane properties were prepared by leading specialists from Asahi Glass Co.10 and by Russian specialists from the Membrane Processes Laboratory in the Karpov Research Institute of Physical Chemistry.11... 

T. Yawataya, Electrochemistry of ion exchange membrane. Properties and application of ion exchange resin membrane, Kogyo Kagaku Zasshi, 1958, 61, 769-774. 

The most important ion-exchange membrane properties are permselectivity and electrical conductivity. The former characterizes the ability of the material to transport only certain ionic species while remaining impermeable to others. The latter measures the propensity of the material to avoid resistance to the passage of ionic current. 

Select Commercially Available Ion Exchange Membrane Properties, eet Corporation. http //www.eetcorp.com/lts/membraneproperties.p)df (May 27, 2013). 

Membranes and Osmosis. Membranes based on PEI can be used for the dehydration of organic solvents such as 2-propanol, methyl ethyl ketone, and toluene (451), and for concentrating seawater (452—454). On exposure to ultrasound waves, aqueous PEI salt solutions and brominated poly(2,6-dimethylphenylene oxide) form stable emulsions from which it is possible to cast membranes in which submicrometer capsules of the salt solution ate embedded (455). The rate of release of the salt solution can be altered by surface—active substances. In membranes, PEI can act as a proton source in the generation of a photocurrent (456). The formation of a PEI coating on ion-exchange membranes modifies the transport properties and results in permanent selectivity of the membrane (457). The electrochemical testing of salts (458) is another possible appHcation of PEI. 

By the time the next overview of electrical properties of polymers was published (Blythe 1979), besides a detailed treatment of dielectric properties it included a chapter on conduction, both ionic and electronic. To take ionic conduction first, ion-exchange membranes as separation tools for electrolytes go back a long way historically, to the beginning of the twentieth century a polymeric membrane semipermeable to ions was first used in 1950 for the desalination of water (Jusa and McRae 1950). This kind of membrane is surveyed in detail by Strathmann (1994). Much more recently, highly developed polymeric membranes began to be used as electrolytes for experimental rechargeable batteries and, with particular success, for fuel cells. This important use is further discussed in Chapter 11. 

Yeager, H. L. Structural and Transport Properties of Perfluorinated Ion-Exchange Membranes 16... 

When we previously investigated the potentiometric properties of carefully purified plasticizers of low polarity, no EMF responses were observed, whereas for a more polar solvent (nitrobenzene), transient EMF responses were obtained [55,59]. Because of this large difference, we were also interested in the combined SHG and EMF response of more polar ion-exchanger membranes. As previously, we used nitrobenzene for this purpose. 

Ion-exchanger membranes with fixed ion-exchanger sites contain ion conductive polymers (ionomers) the properties of which have already been described on p. 128. These membranes are either homogeneous, consisting only of a polyelectrolyte that may be chemically bonded to an un-ionized polymer matrix, and heterogeneous, where the grains of polyelectrolyte are incorporated into an un-ionized polymer membrane. The electrochemical behaviour of these two groups does not differ substantially. 

In Table III the specific conductance and electro-osmotic coefficient (3) for the SPS membrane are shown together with the data for a conventional ion-exchange membrane, AMF C103 (16,17) (polyethylene-styrene graft copolymer containing sulphonic acid groups). It appears that there is a close similarity in properties of both membranes. ... 

Ion-exchange membranes are a new development in the field of ion-selective membranes. By selectivity is understood the property that the transport numbers of the ions in the membranes have values different from those in the free solution. When the transport number of the cations is increased, the membrane is called cation-selective or negative, and the membrane is called anion-selective or positive in the opposite case. 

The name "ion-exchange membrane mainly refers to the fact that this ion-selective property can best be realized by using materials closely resembling the ion-exchange resins. 

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