Dielectric relaxation in concentrated solutions of cis-polyisoprene. Part 2.—Motions of local segments and solvent molecules

Abstract

Dielectric relaxations in concentrated solutions of cis-polyisoprene (cis-PI) in toluene were studied over a wide temperature range. Four loss maxima were observed in the temperature dependence curves of the loss at a given frequency and termed α_I, α_II, β, and γ processes from the high temperature side. The α_I and α_II processes were assigned to the normal mode process and the segmental mode processes of cis-PI, respectively. The intensity of the β process decreased with increasing PI concentration and the loss maximum due to this process disappeared in the range above 50 wt % concentration. Thus, the β process was assigned to the rotation of toluene molecules. The loss maximum of the γ process was observed below the glass transition temperature of toluene and its intensity decreased slightly with increasing PI concentration. We assigned the γ process to the rotational oscillation of toluene molecules in the glassy matrix. The Arrhenius plots of the α_I, α_II, and β processes conformed to the Vogel–Tamman equation. The ratio of the relaxation times of the α_I and α_II processes was approximately independent of temperature.