Surface properties grafting

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). 

Radiation Treatment NVP, 2-hydroxyethylmethacrylate (HEMA), and acrylamide (AAm) have been grafted to the surface of ethylene-propylene-diene monomer (EPDM) rubber vulcanizates using the radiation method (from a Co 7 source) to alter surface properties such as wettability and therefore biocompatibility [197]. Poncin-Epaillard et al. [198] have reported the modification of isotactic PP surface by EB and grafting of AA onto the activated polymer. Radiation-induced grafting of acrylamide onto PE is very important... 

Finally, surface properties of PTFEP were modified photochemically by light-induced grafting of poly(AT,Ar,-dimethylacryl amide) onto the film surface of this material to achieve a remarkable enhancement of its hydrophilicity [513]. 

Most of published results deal with very high graft yield and consequently the bulk properties of the base polymer are altered by grafting. In principle, graft polymerization is an attractive method to impart a variety of surface properties on the condition... 

The surface properties as studied by contact angle measurement are not affected much by the composition of reacting solution so far the solvent is the same. Wettability of all samples plotted in Figures 2 and 3 depends merely on the total amount of graft polymer and the contact angle - IR absorbance plots fall on the same line as shown in Figure 7. 

Solvent Effects on Grafting Rate and Surface Properties. 

We could not conclude at the moment whether the solvent dependent surface properties are to be explained only by the difference in the depth of graft layer. Another possibility is the change in polar group orientation in graft layer as suggested by Hoffman(18). This arguement will be settled by direct determination of the thickness of graft layer prepared under various conditions. Clarification of the surface layer thickness - sur-... 

Takei, Y. G., Aoki, T., Sanui, K., Ogata, N., Sakurai, Y, and Okano, T. Dynamic contact angle measurement of temperature-responsive surfaces properties for poly(Af-isopropylacrylamide) grafted surfaces. Macromolecules, 1994, 27, 6163—6166. 

This problem has also been more durably addressed by modifying the surface properties of the polyolefin materials used to form polymeric sheets, by graft-copolymerizing to those surfaces a monomeric substance which, after copolymerization, confers hydrophilic properties and, in some cases, ion exchange properties. This technique has been found to be practical when the porous substrate is formed from PE, which has been found to lend itself well to a graft-copolymerization reaction of this kind. However, it has been found that when such a reaction is... 

Different pol)uneric materials respond to irradiation by electron beam in different ways. A large number of them will be modified by the formation of a cross-linked network, by changing their surface properties or structure, and some will be degraded. Another field applicable to polymeric systems is polymerization and grafting. Electron beam can also be used for pol5unerization and cross-linking of oligomers and monomers, i.e., in conversion of liquids to solids. 

In materials such as catalysts where surface properties are of importance it should be possible to alter or enhance activity by use of ionizing radiation. Investigations of the possibility of using radiation to achieve graft polymerizations have recently been initiated. For this application ionizing radiation enjoys some very special advantages. 

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