4-vinyl pyridine plasma

The plasma-assisted surface modification of polymers may also serve to create permselective membranes for gas purification. For example, thin membranes of natural rubber treated with a 4-vinyl pyridine plasma are capable of separating O2 from N2 [79]. For additional information on this topic, see Ref. [80]. 

Polyacrylonitrile (PAN) has been used in the preparation of UP membranes for a long time [82, 83] due to its superior resistance to hydrolysis and oxidation. PAN is highly crystalline and relatively hydrophilic and is usually copolymerized with more hydrophilic monomers to improve processability and to make it less brittle. Hollow fibers can be prepared from PAN dissolved in nitric acid [84]. Preparation of PAN membranes by phase inversion from solutions in DMAC, DMF or NMP is also possible. An example is shown in Fig. 4.4. A Sumitomo patent [85] discloses the preparation of membranes from copolymers containing 89% acrylonitrile and 11% ethyl acrylate dissolved in DMF and formamide and coagulated in water. A microporous membrane is obtained. In order to make the membranes suitable for reverse osmosis, they were submitted to a plasma treatment in the presence of 4-vinyl pyridine. 

The heparin Immobilized polyurethane surfaces (prepared by plasma grafting of 1 acryloyl benzotrlazole and subsequent hydrolysis/amlnatlon) are effective In suppressing thrombus formation. The adhesion of peripheral blood mononuclear cells was also lower on such modified surfaces [72]. Heparin immobilized on vinyl pyridine grafted styrene butadiene-styrene block copolymers also shows good biocompatiblllty. The adsorption of albumin and fibrinogen are reduced with the increasing graft levels and heparin content [41]. 

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