Investigation of chemical changes in PMMA induced by 1.6 MeV He+ irradiation by ion beam analytical methods (RBS-ERDA) and infrared spectroscopy (ATR-FTIR)

Abstract

Generally, organic materials are rather sensitive against ionizing radiations. Polymers have exact and known chemical structure, so they are ideal model materials to study ion beam irradiation induced chemical processes. The type and degree of the degradation strongly depend on the chemical groups attached to the main chain of the polymer. However, how these reactions are affected by the characteristics of the irradiation source such as the type of the particle, its energy and the linear energy transfer is not fully understood yet.The aim of this study was the investigation of the chemical effects of He+ ion irradiation on poly(methyl methacrylate) (PMMA) polymer. In-situ Rutherford Backscattering Spectrometry (RBS) and elastic recoil detection analysis measurements (ERDA) were performed simultaneously. In this way, the material loss occurring during irradiation could be followed. Infrared spectroscopy (ATR-FTIR) was applied to monitor chemical changes. With the in situ RBS-ERDA measurements, completed with FT-IR method, a comprehensive radiation chemical analysis could be achieved on the widely used PMMA polymer. Our results concerning the evolution of the hydrogen, carbon and oxygen contents and the changes in chemical groups indicate that a somewhat different radiation chemical mechanism takes place during 1.6 MeV He+ irradiation compared to proton irradiation.