RADIATION-INDUCED REACTIONS IN SWOLLEN POLYMERS. Annual Report
The radioinduced grafting of acrylonitrile onto polyethylene oxide in both in situ and postirradiation cases was investigated. It was found that gamma -irradiation of polyethylene oxide (POLYOX) swollen with acrylonitrile both in the presence and in the absence of benzene resulted in insoluble products which could not be fractionated. Based on infrared analysis, solubility characteristics, and the observed difficulty of inducing postirradiation grafting of acrylonitrile onto Polyox, it was concluded that the irradiated swollen polymer consisted of a completely entangled network of crosslinked polyacrylonitrile and polyethylene oxide chains with a very minor amount, at most, of grafted polymer. Moreover, the dry resin is crosslinked when irradiated in vacuum or in an inert atmosphere such as nitrogen, and is somewhat degraded when irradiated in air. In either case, trapped free radicals are formed in sufficient concentration (4.52 x 10/sup 17//g as measured by electron spin resonance) to make postirradiation grafting possible. However, the maximum amount of such grafting obtained in the polyethylene oxide-acrylonitrile system was only about 1% and 3% of monomer by weight when the polymer was treated in the form of crumb and as thin films, respectively, with ethylene glycol as solvent. A somewhat higher degree of grafting (about 3% acrylonitrile grafted onto Polyox crumb) was obtained with a 50: 50 dimethyl sulfoxide-water mixture as solvent, but even here the extent of reaction was too slight to merit any practical interest in grafting acrylonitrile onto polyethylene oxide. Other monomers employed in postirradiation grafting runs onto Polyox were styrene, vinyl acetate, methyl methacrylate, methyl acrylate, butyl acrylate, acrylic acid, acrylamide, butadiene, and isoprene. Corresponding in situ experiments with most of these polymer monomer combinations produced generally parallel results. Substantial grafting was obtained with acrylamide, less with methyl acrylate and butyl acrylate, and little or none with the remaining monomers. These results support the generalization that polyethylene oxide is a difficult substrate on which to graft vinyl monomers. Nevertheless, in the case of acrylamide, grafts were obtained containing 22.5% and 45% grafted monomer by weight for postirradiation and in situ grafting, respectively. The nuclear magnetic resonance spectra of the latter products showed proton resonance bands which were too broad to permit any determination of microstructure although they supported the estimates of degree of grafting based on nitrogen analysis. From the standpoint of physical properties, postirradiation grafting onto polyethylene oxide produced a relatively insoluble resin which can swell in almost all solvents. However, the initial solubility characteristics of the Polyox resin are such as to make it impracticable to swell it to various controlled extents with different monomers for in situ irradiation. In any event, the latter frequentiy results in a highly insoluble product which is difficult or impossible to characterize. (auth)
- Research Organization:
- Stanford Research Inst., Menlo Park, Calif.
- DOE Contract Number:
- AT(04-3)-115
- NSA Number:
- NSA-17-018108
- OSTI ID:
- 4735978
- Report Number(s):
- TID-18126
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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