Abstract
WHEN plastics, such as polymethylmethacrylate (‘Perspex’), are irradiated with large doses (of the order of 1 Mrad) of ionizing radiations, for example, X-rays or electrons, optical changes can be observed1 and the appearance of electron spin resonance signals2 indicates the formation of free radicals in the solid. In the case of ‘Perspex’ the diffusion of oxygen into the irradiated plastic causes changes in the optical absorption spectrum and information regarding the diffusion process may thus be obtained3. We have found, however, that in the case of ultra-violet-transmitting plasticizer free ‘Perspex’ (kindly provided by Imperial Chemical Industries, Ltd.), when the well-known 4 + 5 line electron spin resonance spectrum 2,4,5 due to the methylmethacrylate free radical was produced by large doses, subsequent exposure of the irradiated sample to an atmosphere of air or oxygen for periods up to 12 weeks at ∼ 25° C. did not lead to a change in the electron spin resonance spectrum which would have corresponded to the formation of a peroxide radical. The 4 + 5 line spectrum persisted slightly weakened and with the ratio of 4 to 5 line spectrum intensity modified.
Similar content being viewed by others
Article PDF
References
Day, M. J., and Stein, G., Nature, 168, 644 (1951).
Schneider, E. E., Day, M. J., and Stein, G., Nature, 168, 645 (1951). Ingram, D. J. E., Free Radicals, 196, 201 (Butterworths, 1958).
Stein, G., Faraday Soc. Disc., 12, 227 (1952). Day, M. J., and Stein, G. (to be published).
Ingram, D. J. E., Symons, M. C. R., and Townsend, M. G., Trans. Farad. Soc., 54, 409 (1958). Abraham, R. J., Melville, H. W., Ovenall, D. W., and Whiffen, D. H., ibid., 1133.
Swallow, A. J., Radiation Chemistry of Organic Compounds, 165 (Pergamon Press, 1960).
Smaller, B., Symp. Free Radicals, Uppsala, 1961 (in the press).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
CARRINGTON, A., STEIN, G. Free Radical Formation and Oxygen Effect in Irradiated Polymethylmethacrylate. Nature 193, 976 (1962). https://doi.org/10.1038/193976a0
Issue Date:
DOI: https://doi.org/10.1038/193976a0
This article is cited by
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.