Radiation-induced reactions with cellulose. IV. Electron paramagnetic resonance studies of radical formation

Abstract

The radiation-induced formation of trapped radicals in cellulose, both in vacuum and air, has been studied by e.p.r, spectroscopy. Factors affecting radical concentration have been examined, including total dose, dose rate, heat, cellulose pretreatment, and kinetics of radical decay. All spectra were asymmetric in shape. Variables affecting line shape have been studied, including oxygen, irradiation conditions such as the presence of water, acetic acid, copper sulphate solution, methanol, ethanol, potassium iodide, and liquid ammonia. The data indicate that the observed cellulose e.p.r, spectrum is composed of an overlapping singlet with a triplet. Studies of radical decay show that a significant concentration of e.p.r. species still remains in irradiated cellulose after 4 years at ambient temperature.