Rotational and translational mobilities of a spin probe in a polymer-solvent system

Abstract

A study has been made of the ratational and translational diffusion of a spi probe, the 2,2,6,6-tetramethylpiperidine-1-oxyl stable radical, in a polymer (SKS-30 rubber) -solvent ( m-xylene) system, whilst varying the polymer concentration from 0 to 100 wt.%. On going from liquid phase to polymer the rotational diffusion coefficient is reduced by 2–2·5 orders, and the translational diffusion coefficient by 3–3·5 orders. Changes in the rotational and translational mobilities of the probe are most marked when the concentration of polymer in solution is >40 wt.%. This stems from an increased local density of the macromolecular units in the low molecular particle region. If a low molecular particle in polymer is displaced to an extent (distance) of the order of its diameter, the number of times it is able to change its orientation is considerably greater in polymer compared with the number in the case of an equal degree of displacement in the liquid phase.