Polyelectrolyte membranes

Drug delivery, dialysis membranes, polyelectrolyte complexes for cell encapsulation, and cell immobilization Complexes for cell encapsulation... 

The dense polyvinyl alcohol layer is supported by a porous PAN substrate membrane. Polyelectrolyte material and chitosan, a natural product, are also potentially useful for dehydration by Silicone... 

Anomalous osmosis Ion-exchange membranes, polyelectrolytes, and osmosis... 

Keywords Fuel cells, Grafting, Membranes, Polyelectrolyte complexes, Sulfo-nated polymers. Surface modification... 

The dense polyvinyl alcohol layer is supported by a porous PAN substrate membrane. Polyelectrolyte material [24] and chitosan [25], a natural product, are also potentially useful for dehydration by pervaporation. Sihcone rubber membranes developed for the removal of organic vapors from air can also be used for the removal of volatile organic compounds (VOCs) from water by pervaporation [23]. Because of the high hydrophobic nature of silicone rubber, VOCs are preferentially sorbed and transported through the membrane. 

Polyelectrolyte multilayers (PEMs) are very important materials due to having a wide range of application helds such as encapsulation of drugs and enzymes, membrane-based separations, antibacterial coatings, membrane reactors and fuel cells. Polyelectrolyte multilayer (PEM) has a wide range of transport properties, simple deposition and small thickness, so it can be used in separation membranes. Polyelectrolyte concentration, duration and temperature of adsorption, deposition and solution pH are key parameters for specific separations. In addition the number of poly electrolyte layers can alter the properties of poly electrolyte. Poly (styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) films are utilized in separation membranes. The adsorption of Cu(II) or Fe(III) ions can be carried out with PSS/poly(allylamine hydrochloride) (PAH) membranes. 

A variety of alternative synthetic strategies has been created for the generation of metal nanoparticles, aU of which make use of different ligands as stabilizers, reverse micelles, microemulsions, membranes, polyelectrolytes, and so on. 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

Polyelectrolyte complex membranes are phase-inversion membranes where polymeric anions and cations react during the gelation. The reaction is suppressed before gelation by incorporating low molecular weight electrolytes or counterions in the solvent system. Both neutral and charged membranes are formed in this manner (14,15). These membranes have not been exploited commercially because of then lack of resistance to chemicals. 

In this lecture we will be concerned by exocytosis of neurotransmitters by chromaffin cells. These cells, located above kidneys, produce the adrenaline burst which induces fast body reactions they are used in neurosciences as standard models for the study of exocytosis by catecholaminergic neurons. Prior to exocytosis, adrenaline is contained at highly concentrated solutions into a polyelectrolyte gel matrix packed into small vesicles present in the cell cytoplasm and brought by the cytoskeleton near the cell outer membrane. Stimulation of the cell by divalent ions induces the fusion of the vesicles membrane with that of the cell and hence the release of the intravesicular content into the outer-cytoplasmic region. 

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. 

A membrane ionomer, in particular a polyelectrolyte with an inert backbone such as Nation . They require a plasticizer (typically water) to achieve good conductivity levels and are associated primarily, in their protonconducting form, with solid polymer-electrolyte fuel cells. 

Polydiallyl-dimethylammonium chloride polymers Polyelectrolytes Polyether glycols Polyethersulfone RO membranes Polyethoxylates, as adjuncts Polyethylene glycol... 

Additional exchange of ion pairs and solvent molecules as in any other membrane formed by polyelectrolytes. 

The chitosan-heparin polyelectrolyte complex was covalently immobilized onto the surface of polyacrylonitrile membrane. The immobilization caused the water contact angle to decrease, thereby indicating an increase in hy-... 

FIG. 1 Geometries of electrolyte interfaces, (a) A planar electrode immersed in a solution with ions, and with the ion distrihution in the double layer, (b) Particles with permanent charges or adsorbed surface charges, (c) A porous electrode or membrane with internal structures, (d) A polyelectrolyte with flexible and dynamic structure in solution, (e) Organized amphophilic molecules, e.g., Langmuir-Blodgett film and microemulsion, (f) Organized polyelectrolytes with internal structures, e.g., membranes and vesicles. 

If 0.6 N lithium bromide is added to the solution of the polyelectrolyte and also to the solvent on the opposite side of the osmometer membrane, the lowermost set of points in Fig. 145 (lower and left scales) is observed. The anion concentration inside and outside the coil is now so similar that there is little tendency for the bromide ions belonging to the polymer to migrate outside the coil. Hence the osmotic pressure behaves normally in the sense that each poly electrolyte molecule contributes essentially only one osmotic unit. The izjc intercept is lower than that for the parent poly-(vinylpyridine) owing to the increase in molecular weight through addition of a molecule of butyl bromide to each unit. 

Ion-exchanger membranes with fixed ion-exchanger sites contain ion conductive polymers (ionomers) the properties of which have already been described on p. 128. These membranes are either homogeneous, consisting only of a polyelectrolyte that may be chemically bonded to an un-ionized polymer matrix, and heterogeneous, where the grains of polyelectrolyte are incorporated into an un-ionized polymer membrane. The electrochemical behaviour of these two groups does not differ substantially. 

The nion term is simply an expression for the osmotic pressure generated across a semipermeable membrane effectively, the gel serves as a membrane which restricts the polyelectrolytes to one phase, while small ions can readily redistribute between phases. Assuming that the ions form an ideal solution, the expression for nion becomes simply... 

One effect of the electrochemical reactions in an aqueous system is a local pH change around the electrodes. By water electrolysis, hydronium ions (H30+) are generated at the anode, while hydroxyl ions (OH ) are produced at the cathode. These changes have been utilized for controlling the permeability of polyelectrolyte gel membrane or on-off solute release via ion exchange or surface erosion of interpolymer complex gels. 

Recently, the LbL technique has been extended from conventional nonporous substrates to macroporous substrates, such as 3DOM materials [58,59], macroporous membranes [60-63], and porous calcium carbonate microparticles [64,65], to prepare porous PE-based materials. LbL-assembly of polyelectrolytes can also be performed on the surface of MS particles preloaded with enzymes [66,67] or small molecule drugs [68], and, under appropriate solution conditions, within the pores of MS particles to generate polymer-based nanoporous spheres following removal of the silica template [69]. 

Polymer complexes associated with two or more complementary polymers are widely used in potential applications in the form of particles, hydrogels, films, and membranes. In particular, a polyion complex (PIC) can be easily formed when oppositely charged polyelectrolytes are mixed in aqueous solution and interact via... 

Y.V. Plekhanova, A.N. Reshetilov, E.V. Yazynina, A.V. Zherdev, and B.B. Dzantiev, A new assay format for electrochemical immunosensors polyelectrolyte-based separation on membrane carriers combined with detection of peroxidase activity by pH-sensitive field-effect transistor. Biosens. Bioelectron. 19, 109-114(2003). 

Suspending enzyme in polymer solution instead of in pure organic solvent not only simplifies preparation of the casting solution, the enzyme suspensions became more uniform and stable. It was also found that at certain concentrations (enzyme, polyelectrolyte, and water) the resulting membranes exhibited extremes in both stability and... 

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