Dielectric relaxation in concentrated solutions of cis-polyisoprene. Part 3.—Relationship between friction coefficient for dielectric normal-mode process and local segmental motions

Abstract

The data of dielectric normal mode process (α_I) and the segmental mode process (α_II) reported in parts 1 and 2 of this series were analysed to find a relationship between the friction coefficient ζ for the normal mode process and the relaxation time τ_s for the segmental mode process. Assuming τ_s proportional to ζ, we attempted to superpose the τ_nvs. molecular weight M_w plots for solutions with different concentrations C. From the vertical and horizontal shift factors, we found that the monomeric friction coefficient ζ_m is approximately proportional to C²τ_s. To explain this result, we assumed that the effective size for the segmental motions expands with decreasing C. The molecular weight M₀ for the unit of the segmental motion was estimated based on the computer simulation reported by Verdier and Stockmayer. The M₀ was found to be 77 for bulk cis-PI and increased with decreasing C approximately in proportion to C^–1.