Separation functional polymeric membranes

Heavy Metal Ion Separation by Functional Polymeric Membranes... 

Following are several commercially available fluoromonomers (1-4) that contain functional groups and have been utilized to make polymeric membranes for ion separations " or as catalysts for aromatic alkylation and acylation reactions. They are also convenient starting precursors, allowing for further functionalization reactions. 

A separator is a porous membrane placed between electrodes of opposite polarity, permeable to ionic flow but preventing electric contact of the electrodes. A variety of separators have been used in batteries over the years. Starting with cedar shingles and sausage casing, separators have been manufactured from cellulosic papers and cellophane to nonwoven fabrics, foams, ion exchange membranes, and microporous flat sheet membranes made from polymeric materials. As batteries have become more sophisticated, separator function has also become more demanding and complex. 

Membrane reactors have been investigated since the 1970s 11). Although membranes can have several functions in a reactor, the most obvious is the separation of reaction components. Initially, the focus has been mainly on polymeric membranes applied in enzymatic reactions, and ultrafiltration of enzymes is commercially applied on a large scale for the synthesis of fine chemicals (e.g., L-methionine) 12). Membrane materials have been improved significantly over those applied initially, and nanofiltration membranes suitable to retain relatively small compounds are now available commercially (e.g., mass cut-off of 400—750 Da). 

Figure 8.24 Oxygen/nitrogen selectivity as a function of oxygen permeability. This plot by Robeson [11] shows the wide range of combination of selectivity and permeability achieved by current materials. Reprinted from J. Membr. Sci. 62, L.M. Robeson, Correlation of Separation Factor Versus Permeability for Polymeric Membranes, p. 165. Copyright 1991, with permission from Elsevier...

Continuous homogeneous catalysis is achieved by membrane filtration, which separates the polymeric catalyst from low molecular weight solvent and products. Hydrogenation of 1-pentene with the soluble pofymer-attached Wilkinson catalyst affords n-pentane in quantitative yield A variety of other catalysts have been attached to functionalized polystyrenes Besides linear polystyrenes, poly(ethylene glycol)s, polyvinylpyrrolidinones and poly(vinyl chloride)s have been used for the liquid-phase catalysis. Instead of membrane filtration for separating the polymer-bound catalyst, selective precipitation has been found to be very effective. In all... 

T. S. Chung, J. J. Shieh, J. Qin, W. H. Lin, and R. Wang, Polymeric membranes for reverse osmosis, ultrafiltration, microfdtration, gas separation, pervaporation, and reactor applications. In Advanced Functional Molecules and Polymers, H. S. Nalwa (ed.). Chapter 7, Gordon Breach, pp. 219-264 (2001). 

We can conclude the following from an Inspection of Figures 20, 21 and 22. Equation 32 gives an accurate pore size distribution function for the porous polymeric membrane prepared by the microphase separation method. The mean radius Increases and the pore size distribution broadens with S. and Pr. The reduced pore distribution N(r)S vs. r/S curve is Independent of S. but dependent on Pr. The effect of Pr on N(r) Is more remarkable than that of S. The reduced pore size distribution curves widen with an Increase In Pr. 

Polymeric nanofibres have found various applications in the biomedical field, such as use of nanofibrous affinity membranes in selective separation, functional wound dressings in wound care and scaffolding materials for tissue repair and regeneration. 

Due to the low preparation cost, monolayer polymeric membranes have been widely used as separators for LIBs. However, limited by the relatively single function of mono-layer polymeric membranes with relatively poor puncture strength and thermal stability, monolayer polymeric membranes may not be able to meet many application demands. 

Monolayer polymeric membranes cannot satisfy all of the optimal characteristics that are related to the LIB safety and performance. Therefore, microporous multilayer separators combining different polymers with different functions have been fabricated. A variety of... 

M. Ulbricht published recently a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane separation processes [121], The author describes novel processing technologies of polymers for membranes, the synthesis of novel polymers with well-defined structure as designed membrane materials, advanced surface functionalization of membranes, the use of templates for creating tailored barrier or surface structures for membranes, and the preparation of composite membranes for the synergistic combination of different functions by different (mainly polymeric) materials. 

Wang, Y.C., Li, C.L., Lee, K.R. and Liaw, D.J. 2005. Pervaporation separation of aqueous alcohol solution through a carbazole-functionalized norbornenederivative membrane using living ring-opening metathesis polymerization. J Memh S l. 246 59-65. 

Figure 12.3 Thermai gravimetric analyses of PEO-PBT multi-block copolymers. Reprinted with permission from Advanced Functional Materials, Tailor-made polymeric membranes based on segmented block copolymers for CO2 separation, by A. Car, C. Stropnik, W.

Figure 12.16 C02/gas selectivity in single gets and different mixed gas as a function of fugacity. (-M- 0% PEC, -O- 10% PEC, -A- 20% PEG, -V- 30% PEC, 40% PEG and 50% PEC. Reprinted with permission from Advanced functional Materials, Tailor-made polymeric membranes based on segmented block copolymers for COj separation, by A. Car, C. Stropnik, W. Yave, K.-V. Peinemann, 23, 2815-2823, Copyright (2008) Wiley-VCH...

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