Polymeric membranes methacrylate

Hydration of polymeric membranes may be influenced by the chemical identity of the polymers. A hydrophilic polymer has a higher potential to hydrate than a hydrophobic one. Sefton and Nishimura [56] studied the diffusive permeability of insulin in polyhydroxyethyl methacrylate (37.1% water), polyhydroxy-ethyl acrylate (51.8% water), polymethacrylic acid (67.5% water), and cupro-phane PT-150 membranes. They found that insulin diffusivity through polyacrylate membrane was directly related to the weight fraction of water in the membrane system under investigation (Fig. 17). 

Hirotsu, T. Graft polymerized membranes of methacrylic acid by plasma for water-ethanol pervaporation. Ind. Eng. Chem. Res. 1987, 26, 1287-1290. 

Yoshikawa, M. and Kitao, T. 1997. Speciality of polymeric membranes-VI. Pervaporation separation of benzene/cyclohexane mixtures through nylon 6-graft-poly(ethyl methacrylate) membranes. 33 25-31. 

In order to solve the problems that occurred with unmodified cellulosic membranes, synthetic membranes were developed. The first synthetic polymeric membrane was produced in the early 1970s. Since that time, various synthetic polymers such as poly-sulfone, polyamide, poly(methyl methacrylate), polyethersulfone, polyethersulfone/ polyamide have been used in the production of synthetic hemodialysis membranes [20,21]. Synthetic membranes have large mean pore size and thick wall structure. These properties provide high ultrafiltration rate, which is necessary for hemodialysis to be achieved with relatively low transmembrane pressures [20]. The main difference in synthetic and cellulosic membranes is the chemical composition of the membrane. Synthetic membranes are made from manufactured thermoplastics, while both modified and unmodified cellulosic membranes are prepared from natural polymers [20]. 

Electric Fuel Ltd. which was modified by the inclusion of an anionic polymeric membrane. The polymeric membrane was composed of interpenetrated network of two polymers. A polycationic cross-linked polyepichlorohydrin was used as the ionic network and poly(hydroxyl ethyl methacrylate) was used as the structural polymer to provide mechanical stability and reduced swelling. The cyclic performance of the cell using a saturated aqueous solution of LiOH and untreated ambient air is shown in Fig. 13b. Relatively high capacities were obtained however, on cycling the lithium metal formed a porous or columnar deposit that increased in volume and caused a loss of contact between the hthium metal and O-LATP [50]. The hfetime of this composite air electrode when used with untreated air in 5 M or saturated LiOH aqueous solution was increased firom 10 h without the anion exchange membrane to 1000 h. 

Graft polymerization of methacrylic acid monomer could increase the hydro-philicity and impart negative charges on the membrane surface. It has been used to remove endocrine disrupting chemicals and pharmaceuticals active compounds [159]. In addition, surface grafting using redox initiation has been developed, which offers simplicity to the process. The reaction can be performed in an aqueous media at room temperature without an external activation [161]. However, redox initiation has relatively slow kinetics that requires a high concentration of monomer [164]. 

Another system under investigation is the iron/ chromium redox flow battery (Fe/Cr RFB) developed by NASA. The performance requirements of the membrane for Fe/Cr RFB are severe. The membrane must readily permit the passage of chloride ions, but should not allow any mixing of the chromium and iron ions. An anionic permselective membrane CDIL-AA5-LC-397, developed by Ionics, Inc., performed well in this system. ° It was prepared by a free radical polymerization of vinylbenzyl chloride and dimethylaminoethyl methacrylate in a 1 1 molar ratio. One major issue with the anionic membranes was its increase in resistance during the time it was exposed to a ferric chloride solution. The resistance increase termed fouling is related to the ability of the ferric ion to form ferric chloride complexes, which are not electrically repelled by the anionic membrane. An experiment by Arnold and Assink indicated that... 

Seki and Tirrell [436] studied the pH-dependent complexation of poly(acrylic acid) derivatives with phospholipid vesicle membranes. These authors found that polyfacrylic acid), poly(methacrylic arid) and poly(ethacrylic acid) modify the properties of a phospholipid vesicle membrane. At or below a critical pH the polymers complex with the membrane, resulting in broadening of the melting transition. The value of the critical pH depends on the chemical structure and tacticity of the polymer and increases with polymer hydro-phobicity from approximately 4.6 for poly(acrylic acid) to approximately 8 for poly(ethacrylic acid). Subsequent photophysical and calorimetric experiments [437] and kinetic studies [398] support the hypothesis that these transitions are caused by pH dependent adsorption of hydrophobic polymeric carboxylic acids... 

Polymeric phospholipids based on dioctadecyldimethylammonium methacrylate were formed by photopolymerization to give polymer-encased vesicles which retained phase behavior. The polymerized vesicles were more stable than non-polymerized vesicles, and permeability experiments showed that vesicles polymerized above the phase transition temperature have lower permeability than the nonpolymerized ones [447-449]. Kono et al. [450,451] employed a polypeptide based on lysine, 2 aminoisobutyric acid and leucine as the sensitive polymer. In the latter reference the polypeptide adhered to the vesicular lipid bilayer membrane at high pH by assuming an amphiphilic helical conformation, while at low pH the structure was disturbed resulting in release of the encapsulated substances. 

Murray et al. (2) prepared permeable membranes for selectively removing phosphate, nitrate, and ferric cations by polymerizing and crosslinking with the modified matrix monomer, (bis-acrylamindo-phenanthroline)dinitrate, (IV), to produce an ion permeability substrate. Kulkami et al. (3) selectively removed cobalt cations from solution using 2-hydroxy ethyl methacrylate copolymers,... 

FIGURE 5.13 Left low MWCO membrane (deionized water 2-methoxyethanol = 3.7 1). Right high MWCO membrane (deionized water 2-methoxyethanol = 0.34 1). The post diameter is 50 pm. For phase-separation polymerization, the monomer is 2-(N-3-sulfo-propyl-N,N-dimethylammonium) ethyl methacrylate, the cross-tinker is methylene bisacry-lamide, and the plotoinitiator is 2,2 -azobis(2-methylpropanimidamide dihydrochloride). To prevent unwanted polymerization that may occur by heat and molecular diffusion outside the UV-irradiated region, a polymerization inhibitor, hydroquinone, is also added. To facilitate covalent attachment of the porous membrane to the silica surface, it is first coated with 3-(trimethoxysilyl)propylacrylate [347]. Reprinted with permission from the American Chemical Society. 

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