ESR study of pressure dependence of free-radical decay in irradiated polystyrene

Radicals giving the usual triplet ESR spectrum have been generated in polystyrene by γ-irradiation at room temperature. The decay of the radicals has been investigated in the temperature interval between 90° and 200° and pressures ranging from 1 to 8000 atm. The effect of pressure on the mechanism of the free-radical decay is discussed. There are two regions of free-radical decay showing different activation volumes: V_I = 11.5 cm³/mole and V_II = 66 cm³/mole. The correlation between molecular motion in the α-relaxation region and radical decay is pointed out.