Paramagnetic probe technique for studying molecular motions in polymers

Abstract

In the paramagnetic probe technique, information about molecular motion in polymers is obtained using stable organic nitroxide radicals incorporated in polymer matrices. Temperature dependence of radical rotation in polymers is well described by Arrhenius equation. For rotation of the radical in polymers, a compensation effect is observed which is related to variation of the actual potential barrier with temperature. Parameters determined by motion of segments are frequencies of radical rotation and actual activation energy. Correlation of segmental motion parameters determined by NMR and paramagnetic probe techniques is noted.