Ion recombination luminescence in polymer glasses induced by electron irradiation. I. High-vinyl polybutadiene

The luminescence of 1,2-polybutadiene was measured during and following irradiation with 1.4-MeV electrons at 900K. Measured under isothermal conditions, the light intensity at first increases sharply on start-up of irradiation, and then reaches a plateau after several seconds. The equilibrium value was found to be linearly dependent on the dose rate employed. The post-irradiation luminescence decay measured at 900K follows second-order kinetics. The light emitted by the irradiated sample during warm-up to room temperature is characterized by the appearance of four intensity maxima at 118, 168, 223, and 2610K. The first three peaks are attributable to the onset of local motion, whereas the peak at 2230K is caused by the long-range motion occurring at the glass-to-rubber transition. A preirradiation of the polymer in vacuo causes an increase in these four peaks as well as the formation of a new maximum at 1430K. Intermittent exposure of the irradiated sample to light of wavelengths lambda > 450 nm causes the isothermal luminescence decay to be interrupted by a burst of light emitted by the sample during and shortly following the light exposure. This treatment also results in considerably reduced intensity maxima during warm-up to room temperature. An interpretation of the findings reported is given on the basis of reactions involving primary and secondary transient species produced during irradiation and on the molecular parameters of the polybutadiene