The role of molecular and radical mobility in the creation of CO2 molecules and OH groups in PADC irradiated with C and O ions

Abstract

We report the loss of carbonate ester and the creation of embedded CO2 molecules and OH groups in poly (allyl diglycol carbonate) (PADC) irradiated with C (11 MeV/u) and O ion (7.5 MeV/u) beams under vacuum at low temperatures (11, 100 and 200 K) and at room temperature (RT) using in-situ FT-IR spectrometry. For comparison with these experiments, the behavior under O ions (6 MeV/u) irradiations in ambient air is examined by off-line FT-IR spectrometry. The radiation chemical yield for loss of carbonate ester (G-carbonate) in PADC irradiated with O ions at 11 K is lower than that obtained at RT. Furthermore, the G value of embedded CO2 molecules (G-CO2) under O ion decreases with decreasing temperature. As CO2 molecules have been said to be formed from the fragmentation of carbonate groups, G-CO2 is compared to G-carbonate. For given temperatures, G-CO2 is significantly lower than G-carbonate. These findings imply that the molecular and radical mobility is crucial for CO2 formation after damage to carbonate groups. As for OH groups, their formation under vacuum is suppressed at low temperatures and a tenuous formation is observed at RT. Oxygen and potentially water molecules, which are present in ambient air, play important roles in the formation of OH groups as new end-points.