Abstract
The electron paramagnetic resonance (EPR) spectra given when polytetrafluoroethylene (PTFE) samples previously irradiated in vacuum are exposed to air, or when PTFE samples are irradiated directly in air have been known since 1955 and are attributed to peroxy radicals. Little attention, however, has been paid to the details of these spectra. EPR measurements at 77°K and 296°K on oriented PTFE samples irradiated in vacuum and then exposed to air are reported. At 77°K, the spectral line shapes can be understood assuming that the radicals are essentially stationary and have an axially symmetric g-tensor with g ∥ = 2.04 and g ⊥ = 2.002. These values are compared with those of other radicals in which the unpaired electron is thought to be located mainly on an oxygen atom. At 296°K, the spectra are narrower, showing the occurrence of motion. This is probably an oscillation about the polymer chain axis.
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