Poly , glow-discharge

Applications to polymer chemistry have also been proposed. Interestingly. the adhesion toward itself. Al or stainless steel, of polythene or TeHon with epoxyresins adhesives is considerably improved by a glow discharge polymerization of methane (or etheiie. ethyne) on the polymer surface, CH4 giving the best results (33). Such a modification of polymer surfaces has also received attention within the scope of modifying poly mer membrane compatibility with blood for medical applications. Various o nic compounds (even CH4 > have been studied in this context, where an ultrathin layer (< 1000 is sufficient to alter blood compatibility 134). 

Figure 9.3 Weight loss as a function of exposure time with oxygen glow discharge POM polyoxymethylen, PMMA poly(methyl methacrylate), PET poly(ethylene terephthalate), LDPE low density polyethylene, SR silicone rubber (polydimethylsiloxane).

The formation of a polymer in a glow discharge is a complex phenomenon, and the interpretation of the formation mechanism is not at all clarified by the misapplication of the term "polymerization". The term "polymerization" is generally accepted to mean that the molecular units (monomers) are linked together by the "polymerization" process. Consequently, the resultant polymer is conventionally named by using the prefix "poly" plus the name of the monomer. For instance, the polymer formed by the polymerization of styrene is referred to as polystyrene. In other words, "polymerization" conventionally refers to mole-... 

XPS-analysis of surface exposed to the perfluorinated monomers showed the presence of all possible species regardless of monomer structure. Fig. 1 shows the deconvoluted carbon Is XPS spectrum of a poly(ethylene) surface after exposure of hexafluoropropylene in a glow discharge. A 1 1 1 ratio of the CF3, CF2 and CF groups was found suggesting the structure of a normal addition polymer. 

Monomers Not Polymerizable by Plasma Initiation. When styrene and a-methy1styrene were subjected to plasma treatment, the monomers became yellowish and only trace amounts of insoluble films were formed. The discoloration was intensified and extensive formation of dark films were observed if carbon tetrachloride was added as the solvent. No post-polymerization was detectable for these monomers. Generally styrene and a-methylstyrene readily undergo thermal polymerization. However, no thermal polymerization was possible for these monomers after having been subjected to plasma treatment for one minute or less. It has been demonstrated from the emission spectra of glow discharge plasma of benzene (6) and its derivatives (7 ) that most of the reaction intermediates are phenyl or benzyl radicals which subsequently form a variety of compounds such as acetylene, methylacetylene, allene, fulvene, biphenyl, poly(p-phenylenes) and so forth. It is possible that styrene and a-methylstyrene also behave similarly, so that species from the monomer plasma are poor initiators for polymerization. 

Y J Kim, 1K Kang, M W Huh and S C Yoon, Surface characterization and in vitro blood compatibility of poly (ethylene teiephthalate) immobilized with insulin and/or heparin using plasma glow discharge, Biomaterials, 1999 21(2) 121-30. 

Hudis, M. and Prescott, L.E., Surface Crosslinking of Polyethylene Produced by the Ultraviolet Radiation From a Hydrogen Glow Discharge , Poly. Letters, 10, 179-183 (1972)... 

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