Study of free radicals in irradiated PMMA (doped or undoped) using ESR spectroscopy

In our last study we developed the properties of PMMA doped with squalene permiting to find the absorbed dose and the duration separating the irradiation and the measurement. Electron spin resonance (ESR) appears to be well suited for the elucidation of the mechanism of radiolysis and could permit to explain the difference between doped and undoped dosimeter. In this paper, we analyse the evolution of the ESR signal of PMMA (with or without squalene) as a function of time and thickness. The free radical decay appears, between the doped dosimeters, only different for 2 mm thickness and this study presents evidence for the role of oxygen and free radical diffusion in the PMMA matrix.