Glassy membranes

Fig. 38. Permeability as a function of molar volume for a mbbery and glassy polymer, illustrating the different balance between sorption and diffusion in these polymer types. The mbbery membrane is highly permeable the permeability increases rapidly with increasing permeant size because sorption dominates. The glassy membrane is much less permeable the permeability decreases with increasing permeant size because diffusion dominates (84).

Vassilev VS, Boycheva SV (2005) Chemical sensors with chalcogenide glassy membranes. Talanta 67 20-27... 

This chapter is concerned with processes that lead to formation of ISE membrane potentials. The membrane potentials of electrodes with liquid membranes containing a dissolved ion-exchanger ion or a dissolved ionophore (ion carrier), and of electrodes with solid or glassy membranes will be considered. More complicated systems, for example ISEs with a gas gap and enzyme electrodes, will be discussed in chapters 4 and 9. 

The use of ISEs in non-aqueous media(for a survey see [125,128]) is limited to electrodes with solid or glassy membranes. Even here there are further limitations connected with membrane material dissolution as a result of complexation by the solvent and damage to the membrane matrix or to the cement between the membrane and the electrode body. Silver halide electrodes have been used in methanol, ethanol, n-propanol, /so-propanol and other aliphatic alcohols, dimethylformamide, acetic acid and mixtures with water [40, 81, 121, 128]. The slope of the ISE potential dependence on the logarithm of the activity decreases with decreasing dielectric constant of the medium. With the fluoride ISE, the theoretical slope was found in ethanol-water mixtures [95] and in dimethylsulphoxide [23], and with PbS ISE in alcohols, their mixtures with water, dioxan and dimethylsulphoxide [134]. The standard Gibbs energies for the transfer of ions from water into these media were also determined [27, 30] using ISEs in non-aqueous media. 

ION-SELECTIVE ELECTRODES WITH SOLID OR GLASSY MEMBRANES... 

Table 3.3 Effect of fluorination on the carbon dioxide/methane selectivity of various glassy membrane materials...

Figure 8.30 The relative size and condensability (boiling point) of the principal components of natural gas. Glassy membranes generally separate by differences in size rubbery membranes separate by differences in condensability...

Figure 21.4 Porous membranes developed for emulsification processes, (a) Shirasu porous glassy membrane (from SPG Technology Co., LTD, Japan), (b) metallic membrane (From Micropore Technologies, United Kingdom).

For the separation of permanent gases, nse glassy membranes with higher selectivity and lower permeability. 

The external epithehal root sheath is composed of several layers of ceUs similar to the epidermis, with which it is continuous in the upper portion of the folhcle. External to this layer is a homogeneous glassy membrane corresponding to the basal lamina of the epidermis. The entire epithehal root sheath (internal and extanal) is enclosed by a dermal root sheath composed of collagen and elastic hbers richly supplied by blood vessels and nerves, especially in the dermal papilla. 

Modelling Gas Solubility Into Mixed Matrix Glassy Membranes... 

Gas concentration within glassy membranes consists of gas within the polymeric matrix as well as adsorbed in the microvoids. Therefore, the total concentration of absorbed gas within a glassy membrane (C) can be described by [15] ... 

Hence, the dual-mode sorption for glassy membranes is written as ... 

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