Postirradiation polymerization and ESR studies of γ‐irradiated N‐tert‐butylacrylamide

Abstract

AbstractPostirradiation polymerization of γ‐irradiated N‐tert‐butylacrylamide was studied at 80, 85, 90, and 100°C, and the activation energy was found to be 183 kJ · mol−1. By ESR spectroscopy, the half‐life for the second order decay of the irradiated monomer was found to be 13,8 h at 25°C with a decay rate constant of 4,5 · 106 g · mol−1 · h−1. The effect of oxygen and sulfur dioxide on γ‐irradiated N‐tert‐butylacrylamide was also studied. It was observed that oxygen reacts with N‐tert‐butylacrylamide free radicals resulting in a characteristic peroxyl radical spectrum. The signal decays rapidly and disappears in about 100 h. The decay was found to be of second order with a rate constant of 1,3 · 107 g · mol−1 · h−1 and a half‐life of 3,8 h at 25°C. In contrast to the situation with atmospheric oxygen, an appreciable fraction of the free radicals does not react rapidly with sulfur dioxide. The changes in the ESR spectra indicate that at least a large fraction of the original N‐tert‐butylacrylamide radicals, generated in the irradiated sample, react with sulfur dioxide rapidly to give sulfonyl radicals. Their decay is second order with a rate constant of 4,5 · 106 g · mol−1 · h−1 and a half‐life of 8,3 h.