FLUORESCENCE DEPOLARIZATION STUDY OF THE GLASS-RUBBER RELAXATION IN A POLYISOPRENE

The glass-rubber relaxation of an anionic poly(cis-l, 4-isoprene) is investigated in the range of 10-7-10-9 s, using a fluorescent label bonded within the chain backbones and several probes of varying size dissolved in the polymer matrix. Fluorescence depolarization allows appropriate models of rotational Brownian motion to be checked and relaxation times to be calculated as a function of temperature. Label and large probes are shown to reflect the glass-rubber relaxation in agreement with the WLF equation. The size dependence of the probe relaxation times is also analyzed. When the label and probe relaxation times are compared, the smallest chain segments involved in the glass-rubber relaxation seem to be composed of about five monomer units. © 1979, American Chemical Society. All rights reserved.