Electron spin resonance studies on internal motion and conformation of polyphenoxy radicals

Abstract

A comparative study is made of a series of polymeric 4-aryloxyphenoxy radicals (polyphenoxy radicals) and a series of 4-methoxyphenoxy radicals. Most polyphenoxy radicals show hyperfine coupling of the protons of the first ring of the polymer chain only; moreover, the ortho couplings are inequivalent at 20°C. At higher temperatures symmetric line-width effects are often observed, indicating fast internal motion. The nature of the motions is discussed. Hyperfine coupling with second-ring protons is observed in the poly-2,3,5,6-tetramethylphenoxy radical. Approximate conclusions about equilibrium conformations and spin distribution are drawn.