Radiation-induced oxidation of syndiotactic 1,2-polybutadiene

The γ-ray-induced oxidation of syndiotactic 1,2-polybutadiene film with the thickness of 15 μ was carried out at 30 -- 1000C in air atmosphere. The weight of the film increased linearly with the radiation dose after some induction period. Infrared spectroscopy showed the decrease of vinyl group and the formation of various oxygen-containing groups such as alcohol, hydroperoxide, unsaturated ketone, acid, saturated ketone, aldehyde, ester and peracid groups. Among the carbonyl groups, the saturated ketone group was predominant. In the early stage of the oxidation, the rates of both weight increase and formation of hydroxy and carbonyl groups were found to be approximately proportional to the square root of dose rate. These rates also increased with the increase of irradiation temperature and the apparent activation energies for the formation of hydroxy and carbonyl groups were determined to be 5 -- 6 kcal/mol. Further, it was found that post reaction proceeded gradually when the film irradiated at 300C was kept in air without irradiation. On the basis of these results, the oxidation mechanism was discussed in connection with the cyclization and crosslinking of the polymer. (auth.)