Separation using functional polymeric

Tomoi, M. and W. T. Ford, Polymeric Phase Transfer Catalysts, Chap. 5 in Synthesis and Separations Using Functional Polymers, D. C. Sherrington and P. Hodge, eds., Wiley, New York, 1988. 

Widdecke H., Design and industrial application of polymeric acid catalysts, in D. C. Sherrington, P. Hodge (Eds.), Syntheses and Separations using Functional Polymers, Wiley, Chichester, 149 (1988)... 

Fluorinated polymers, especially polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE) with hexafluoropropylene (HFP) and perfluorinated alkyl vinyl ethers (PFAVE) as well as other fluorine-containing polymers are well known as materials with unique inertness. However, fluorinated polymers with functional groups are of much more interest because they combine the merits of pefluorinated materials and functional polymers (the terms functional monomer/ polymer will be used in this chapter to mean monomer/polymer containing functional groups, respectively). Such materials can be used, e.g., as ion exchange membranes for chlorine-alkali and fuel cells, gas separation membranes, solid polymeric superacid catalysts and polymeric reagents for various organic reactions, and chemical sensors. Of course, fully fluorinated materials are exceptionally inert, but at the same time are the most complicated to produce. 

POE 6000 was used as polymeric support, a soluble polyethylene glycol derivative functionalized at both termini with an amino group and with an average molecular mass of 6000 Da [62-63]. After completion of the homogeneous reactions it can be precipitated, filtered off, and washed with diethyl ether, thereby facilitating the separation of surplus reagents and the side products. Furthermore it allows for NMR spectroscopic monitoring of the reactions [64]. 

Porous materials used for chromatography result from a chemically induced phase separation using chain-wise polymerization of vinyl-containing monomers crosslinked with a portion of divinyl functional monomers. Frechet has improved this technique for the preparation of porous PS beads [48]. In this approach the inner phase consists of a mixture containing the reactive styrene and divinylbenzene monomers as well as an unreactive polymeric porogen. After polymerization, the soluble polymeric porogen is removed, leaving behind ma-croporous beads with pore sizes of around 100-500 nm. 

The use of a convective macroporous polymer as an alternative support material instead of silica for the preparation of protein-based CSPs has successfully been demonstrated by Hofstetter et al. [221]. Enantioseparation was performed using a polymeric flow-through-type chromatographic support (POROS-EP, 20 pm polymer particles with epoxy functionalities) and covalently bound BSA as chiral SO. Using flow rates of up to 10 ml/min, rapid enantiomer separation of acidic compounds, including a variety of amino acid derivatives and drugs, could be achieved within a few minutes at medium efficiencies, typical for protein chiral stationary phases (Fig. 9.13). 

As the membrane acts as a separating medium between two flow compartments, these basic functions can be applied to liquid/liquid, gas/liquid and gas/ gas systems, respectively. The physical shape of the membrane strongly depends on the membrane material used. For polymeric systems, these can be flat sheets in a plate-and-frame configuration, spiral-wound modules, and tubular mem-... 

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