Polyelectrolyte complex ultrafiltration membranes

A variety of synthetic polymers, including polycarbonate resins, substituted olefins, and polyelectrolyte complexes, are employed as ultrafiltration membranes. Many of these membranes can be handled dry, have superior organic solvent resistance, and are less sensitive to temperature and pH than cellulose acetate, which is widely used in RO systems. 

Polyelectrolyte complex membranes are phase-inversion membranes where polymeric anions and cations react during the gelation. Inorganic ultrafiltration membranes are formed by depositing particles on a porous substrate. Dynamic membranes are concentration polarization layers formed in situ from the ultrafiltration of colloidal material analogous to a precoat in conventional filter operations. Track-etched membranes are made by exposing thin films (mica, polycarbonate, etc.) to fission fragments from a radiation source. 

As noted previously (see Chap. 3), the membranes of intermacromolecular complexes (especially polyelectrolyte complexes) have specific characteristics such as permeability to water, small molecules and gases. Therefore, ultrafiltration membranes are most useful applications of these intermacromolecular complexes. Considerable interest has consequently developed in the use of... 

The membranes produced from polyelectrolyte complexes on the basis of weak polyelectrolytes, e.g. poly(carboxylic adds) (PAA and PMAA) and polyamines [poly(2-N,N-dimethylaminoethyl methacrylate), polyethylenepiperidine, polyethyl-enepyperasine, polyethylenimine] have been prepared140,141 and used in dialysis and ultrafiltration. Permeability coeffirients of membranes made from poly electrolyte complexes are much higher (4 and 20 times, resp.) in comparison with the cellulose-based membranes (Cuprophane, Film 1(M)). 

Polyelectrolyte complexes are very promising materials for preparing semi-permeable membranes of definite permeability and selectivity The methods of preparation and the properties of membranes made of polyelectrolyte complexes based on strong polyelectrolytes, e.g. poly(sodium sterene sulfonate) and poly(vinylbenzyl-trimethyl ammonium chloride) were described These membranes may be applied for reverse osmosis in the desalting of sea-water, for dialysis and ultrafiltration in purifications and concentration of water solutions containing coUoids or micro-and macroparticles ... 

Complexes based on weak polyelectrolytes are used in dialysis and ultrafiltration due to their superior permeability coefficients compared with cellulose-based membranes. Potential uses In the areas of artificial tissues and as blood vascular... 

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