Electron spin resonance study of spin exchange in a nematic solvent

Abstract

Spin-exchange rate constants have been measured from the concentration dependence of the e.s.r. linewidths of two nitroxide radicals, TANONE (4-oxo-2,2,6,6-tetramethylpiperidino-oxy) and M-DOXYL [2-hexyl-2-(10′-methoxycarbonyldecyl)-4,4-dimethyloxazolidinyl-3-oxyl], in the isotropic and nematic phases of MBBA. Strong exchange is observed for TANONE in both phases and for M-DOXYL in the isotropic phase but the latter radical exhibits weak exchange in the nematic phase. A qualitative discussion of the nature of the radical–radical encounters affords an explanation of the observations.