Atmosphere and dose effects on the SHI irradiation of atactic polystyrene

This article deals with Swift Heavy Ion (SHI) irradiation of atactic polystyrene at different doses, up to about 10 MGy, under an inert and oxidative atmosphere. The effect of the irradiation is analyzed using various tools such as high-resolution gas mass spectrometry, gel fraction, size exclusion chromatography, and Fourier Transform InfraRed spectroscopy. Previous research has shown that under SHI and in conditions of homogenous oxidation, two kinds of defects can be identified: those commonly observed under an oxidative atmosphere with low linear energy transfer irradiations (hydroperoxides and carbonyl bonds, for instance), and those evidenced under inert atmosphere (C=C bonds ...). These latter defects are assigned to the heterogeneous structure of energy depo-sition with ion beams because of ion tracks' high ionization and excitation density. Polystyrene (PS) is known to be very radiation-resistant under inert atmosphere. Although degradation is increased under oxidative atmo-sphere, the oxidation remains very low compared to the one observed in polyethylene, even at doses as high as 10 MGy. The global low oxidation of PS under oxidative atmosphere is explained, as under inert atmosphere, by the presence of aromatic rings that confers efficient radiation resistence to the polymer.