Poly membranes permselectivity

The current state-of-the-art proton exchange membrane is Nafion, a DuPont product that was developed in the late 1960s primarily as a permselective separator in chlor-alkali electrolyzers. Nation s poly(perfluorosulfonic acid) structure imparts exceptional oxidative and chemical stability, which is also important in fuel cell applications. 

I. Pinnau, Ultrathin Ethyl Cellulose/Poly(4-methyl pentene-1) Permselective Membranes, US Patent 4,871,378 (October 1989). 

Except poly(dimethylsiloxane), all of the conventional polymers such as cellulose acetate, poly(phenylene oxide), nylon, polyethylene, and nafion are known to permeate water preferentially against ethanol111,112). However, in order to separate ethanol from dilute aqueous solution, it is favorable to use a membrane which permeates ethanol preferentially (ethanol-permselective membrane). 

FIGURE 9.10 Dependence of ideal hydrocarbon/nitrogen permselectivity on the boiling temperature of the hydrocarbons for a poly-organosihcon membrane produced by GKSS [39-43]. (From Semenova, S.I., J. Membr. Set, 231, 189, 2004. With permission.)... 

The formation of microcapsules Is only one example of the use of polyelectrolyte complexes. Another example Is the formation of a permselective membrane around live cells by a complex formed between alginate and poly(L-lys1ne)(55). This complex 1s formed under mild conditions so as not to harm the cells, and the membrane can be tailored so that It 1s permeable to cell nutrients, but Impermeable to the cellular products. This process 1s of interest to those concerned with large-scale cell cultures. 

Liquid membrane electrodes are three (or four) component membrane based devices with positively charged, negatively charged, or electrically neutral ionophores. The main component of the liquid membrane is the ionophore, or mobile carrier—a compound with binding properties to different ions and responsible for the ion selectivity. The carriers are incorporated into membrane matrices, most commonly into plasticized poly(vinyl chloride). Liquid membranes often contain lipophilic salt additives also to enhance the permselectivity of hte membrane. 

To further confirm the effect of the tightness of the anion exchange membrane on permselectivity between anions, anion exchange membranes have been prepared by the reaction scheme shown in Figure 5.22.91 Namely, copolymer membranes composed of chloromethylstyrene and divinylbenzene are reacted with 4-vinylpyridine to form poly(4-vinylpyiridinium) in the cross-linked membrane matrix and then with trimethylamine to aminate the remaining chloromethyl... 

In general, iodide ions selectively permeate through anion exchange membranes.110 The transport number of iodide ions relative to chloride ions of a typical anion exchange membrane is 4.8. After the formation of a poly(N-n-dodecyl-vinylpyridinium) bromide layer on the desalting side of the same membrane, Pci1 attains 35.5, representing an iodide ion permselective mem-... 

Pervaporation is a method of separating liquid mixtures, especially ethanol-water mixtures, withtheuseofapolymermembrane. Poly(TMSP)membranehasprovedhighlypermselective for ethanol in the ethanol-water pervaporation. Thus, the separation factor, a(EtOH/ H2O), reaches 17 at 10 wt% ethanol in the feed. This value is similar to that for poly(dimethylsiloxane), a well-known ethanol-permselective membrane. In contrast, other substituted poly acetylenes are nonpermselective or rather water-permselective. On the basis of its excellent adsorptivity for organic compounds, poly(TMSP) has been applied to a regenerate column packing which removes trace organic solvents from water ". ... 

On carbon films prepared fi om commercially available poly(imide) films with a thickness of 0.1 mm, selective permeation of hydrogen gas was recently found [105]. This permselectivity may help to develop applications of these carbon films in fuel cells for vehicles, since CO in H2 gas supplied from an on-board reformer has to be removed through a molecular sieving membrane. 

A trimethylsilyl or trifluoromethyl group containing poly(phenylacetylenes) for oxygen and ethanol permselective membranes had been prepared by WCle and a Rh complex [Rh(cyclooctadiens) (triphenyl-phosphine) 2] PFe (RhP). ... 

A.M. Dessouki, N.H. Taher, M.B. El Arnaouty, Synthesis of permselective membrane induced grafting of N-vinyl-pyrrolidone onto poly(tetraffuoroethy-lene-hexaftuoropropylene-vinylidene fluoride) (TFB) films. Polymer International 48 (1999) 92, 67. 

Komatsuka, T. and Nagai, K. (2009) Temperature dependence on gas permeability and permselectivity of poly(lactic acid) blend membranes. Polymer Journal, 41, 455-458. 

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