Abstract
It is well known that when polymeric materials were irradiated by high-energy radiation, the polymeric materials produced numbers of free radicals. In this paper, we want to study the free radicals of poly(methyl methacrylate) (PMMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) irradiated by Co60 Gamma-ray and use the electron paramagnetic resonance (EPR) to observe these two materials. The major radicals of irradiated PMMA are the 5-line, 4-line and broad single line radicals. The major radicals of irradiated PHEMA are the 4-line, 3-line and broad single line radicals. The concentrations of these radicals decrease during isothermal annealing. The 5-line and 4-line radicals of PMMA and the 4-line and 3-line radicals of PHEMA all follow the second-order annihilation process during isothermal annealing. The condition of the broad single line radicals of PMMA and PHEMA is more complicated. It seems that they follow the first-order annihilation process at the short times and then follow the second-order annihilation process at the long times. The structures of the 5-line and 4-line radicals of PMMA and the 4-line and 3-line radicals of PHEMA are well resolved but it is difficult to understand the structures of the broad single line radicals of PMMA and PHEMA.