ESR study of the rotational mobility of spin labels and spin probes in divinyl rubber (in the two millimetre and three centimetre ranges) together with investigations based on the electron spin echo and dielectric relaxation methods

Abstract

The mobility of a spin label stably bound to SKD macromolecules has been investigated witthin the correlation time intervals 5 × 10 −11−3 × 10 −4 sec. In addition, the mobility of a spin probe introduced into the rubber has been studied. At high temperatures the mobility of the probe exceeds that of the label by a factor of ∼2, whereas in the region of the glass transition temperature T g the difference in their mobility is insignificant. With regard to α relaxation processes the dielectric relaxation times for the spin probe and for the divinyl rubber are in good agreement with characteristic times of rotational mobility determined at high temperatures by ESR for the probe and the label. In the area of slow motions stationary methods of ESR indicate the high-frequency branch of the characteristic times distribution for the β relaxation process, while the electron spin echo method indicates the low-frequency branch.