The effects of γ-radiation on polyacrylonitrile

The effect of γ-radiation on polyacrylonitrile has been examined using ESR spectroscopy and through analysis of the changes in molecular weight. The G-values for radical formation of polyacrylonitrile have been calculated at 77 and 300K; G(R ·) ≅ 2·8 at 77K and G(R ·) ≅ 4·2 at 300K. The ESR spectrum at 300K was assigned primarily to two radicals; one resulting from H abstraction from the methylene group, to form a chain radical, and the other from radical addition to the nitrile group, to form a polyimine radical. These radicals are consistent with a dominant cross-linking reaction. The G-values for cross-linking and scission have been determined at 300K; G(S) ≅ 0·0 and G(X) ≅ 0·59. The cross-linking possibly results from addition of backbone radicals to nitrile groups on adjacent chains.