The dielectric relaxation spectrum
g(τ) for undiluted cis-polyisoprene (cis-PI) was compared with the shear stress relaxation spectrum
H(τ). The peaks of
g(τ) due to the normal mode and the segmental mode processes corresponded well to the peaks of
H(τ) located in the terminal and transition regions, respectively. Thus, the mechanical relaxation process around the maximum of the wedge shaped spectrum was assigned to the local segmental motions.
The longest relaxation time, τ
R(
Mc), for the polymer chains having the characteristic molecular weight
Mc was compared with the relaxation time, τ
s, for the dielectric segmental mode process. The ratio, τ
R(
Mc)/τ
s, was found to be approximately 2×10
4 independently of the chemical structure of polymers. From this relation, the frictional coefficient, ζ, for a monomer unit was expressed as
ζ=3400
mTρτ
s/
Mc where
m is the number of backbone atoms in the monomeric unit and ρ the density.
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