CHEMICAL MODIFICATION OF PMMA BY MEV AND GEV, LIGHT AND HEAVY, ION IRRADIATIONS

Chemical modification of the polymers polymethylmethacrylate (PMMA) and polymide (PI) irradiated with MeV and GeV ion beams has been studied using infrared absorption spectroscopy. Whilst at GeV energies heavy ion irradiation results in a greatly enhanced production of aromatic compounds, at lower energies destructive chemical mechanisms dominate. There are indications of an energy threshold value corresponding to the required energy density transferred, above which molecular construction surpasses destruction processes. The formation of ring structures in organic solids at high transferred electronic energy densities may be an early step in a growth chain reaction similar to that which gives rise to fullerene creation along high energy ion tracks in materials very rich in carbon.