Dielectric Relaxation of Type-A Polymers in Melts and Solutions

Dielectric Behavior of cis-Polyisoprene in Carbon Dioxide under High Pressure

“…(2)) This phenomenological expression for {ε 0 −ε'(ω)}/Δε and ε"(ω)/Δε is formally identical to the expression of storage and loss moduli G'(ω) and G"(ω) in terms of the relaxation spectrum. 7,8) Thus, relationships similar to those for the moduli hold for the dielectric {ε 0 −ε'(ω)}/Δε and ε"(ω)/Δε ; for example, the terminal dielectric relaxation time (= secondmoment average relaxation time) can be evaluated as 6) The global dynamics of the type-A chains is reflected in both dielectric and viscoelastic relaxation processes in long time scale. This feature enables us to examine the global dynamics through the dielectric method (instead of the viscoelastic method), as attempted in this study.…”

“…6) For convenience of later discussion, we † To whom correspondence should be addressed. E-mail: matsmiya@scl.kyoto-u.ac.jp here briefly summarize the molecular expression of dielectric quantities of these chains.…”

“…For the PIP chains having non-inverted type-A dipoles and being subjected to a static electric field at time t < 0, the normalized dielectric relaxation function Φ(t) after removal of this field (at t ≥ 0) detects the orientational memory decay of their end-to-end vector R(t), 5,6) The dynamic dielectric constant ε'(ω) and dielectric loss ε"(ω), measured against an oscillatory electric field of angular frequency ω, are expressed as the Fourier transformation of the time-derivative of Φ(t),…”

“…In general, the orientational memory of flexible chains decays through a series of relaxation modes (reflecting the chain motion at various length scales) and Φ(t) is expressed as a sum of the contributions from these modes as 6) Here, g p and τ ε,p (τ ε,1 > τ ε,2 > τ ε,3 ...) are the normalized intensity and characteristic time for the p-th dielectric mode.…”

“…PIP has permanent electrical dipoles parallel along and perpendicular to its contour (so-called type-A and type-B dipoles 5,6) ) thereby exhibiting the dielectric dispersions due to their global and local motion at low and high frequencies. In our experimental window, the dispersion due to the global motion was detected.…”