Hydrophilic polymers polyacrylamide

Support materials for low-pressure affinity chromatography include agarose (cross-linked with epichlorohydrin), cellulose, dextran, silica, and polyacrylamide 62 in HPLC a rigid, highly porous, hydrophilic polymer is typically used. Large pore sizes are necessary, as either the analyte or the affinity ligand are macromolecules. To provide unhindered access of... 

An ideal matrix for gel filtration should consist of partides of a hydrophilic polymer, that is as inert as possible, as rigid as possible, uncharged, and of uniform size (Patel 1993). Suitable materials are naturally occurring polymers, such as agarose or dextran, which have been stabilised by chemical cross linking, and also synthetic polymers such as polyacrylamide. These materials are available as spherical partides of different diameter (10-500 pm) and pore sizes the pore size determines the range of optimal molecular weight separation (Table 4-1). 

These dressings are sheets of three-dimensional networks of cross-linked hydrophilic polymers (polyethylene oxide, polyacrylamides, polyvinylpyrrolidone, carboxymethylcellulose, modified corn starch). Their formulation may incorporate up to 96% bound water, but they are insoluble in water and they interact by three-dimensional swelling with aqueous solutions. The polymer physically entraps water to form a solid sheet and they have a thermal capacity that provides initial cooling to the wound surface. A secondary dressing is required. 

Polyacrylamide (PAAm) is a hydrophilic polymer that absorbs and retains large volumes of water. However, aqueous solutions of PAAm, especially the high molecular weight species, undergo physical aging, which results in a decrease in viscosity. PAAm is soluble in hydrophilic non-aqueous liquids such as glycerol, but insoluble in methanol and ethanol. 

Contrary to PS, polyacrylamide is a hydrophilic polymer. This may increase the ligand exchange rate, i.e., the column efficiency. Thus on the polyacrylamide-CH2-L-proline-Cu(II) macroporous microspheres, the enan-... 

Fig. 1 Structures of some common synthetic hydrophilic polymers (A) poly aery lie acid, (B) polymethacrylic acid, (C) polyhydroxyethyl methacrylate, (D) polyvinyl alcohol, (E) polyvinyl acetate, (F) PEG/PEO, (G) polyacrylamide, (H) polyvinylpyrrolidinone, (I) Nylon 6, and (J) a simple polyurethane.

Polyacrylamides are also suitable for a variety of biomedical uses the structure of polyacrylamide is shown in Fig. IG, although the use of acrylamides in copolymers is much more common. Polyvinylpyrrolidinone has also found use as a biocompatible coating material (Fig. IH). Polyacrylonitrile, though not suitable in itself, can be hydrolyzed to form some hydrophilic polymers such as the Hypan (Hymedix Inc.) series of hydrogels. 

Supports based on synthetic hydrophilic polymers such as polyvinyl alcohol and polyacrylamide or natural polymers like agarose have been developed. 

Many natural hydrogels are known to be constituents of the extracellular matrix, mucin, glycocalix and so on. Jelly is a well-known example of the use of hydrogels in food. Hydrogels can be obtained from many hydrophilic polymers, either natural (e.g. cellulose, dextran, alginate, hyaltuonic acid, chitosan, pectin) or synthetic (e.g. poly(vinyl alcohol) (PVA), PEG, poly(vinyl pyrrolidone) (PVP), PHEMA, polyacrylamides). 

Contrary to PS, polyacrylamide is a hydrophilic polymer. This may increase the ligand exchange rate, i.e., the column efficiency. Thus on the polyacrylamide-CH2-L-pro-line-Cu(II) macroporous microspheres, the enantiomers of valine, threonine, isoleucine, serine, phenylalanine, tyrosine, tryptophan, and asparagine were completely resolved in less than 1 hr with water as the eluent. The efficiency was markedly improved. However, the methylene bridge between the ligand and the matrix was not stable under acidic and basic conditions. The same sorbent, but with a long spacer, -CH2CH20CH2CH(0H)CH2-, was prepared with L-proline content 1.76 mmol/g of dry polymer." When the polymer was soaked in 0.1 M HCl, 0.1 M NaOH or 1 M NH3, aqueous solutions, respectively, at... 

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