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Viscoelastic behavior of PVC gels/sols in a wide range of PVC concentration c was examined in various plasticizers having different solubility toward PVC. The gel point c g decreased with decreasing solubility, possibly due to enhanced formation of PVC crystallites (crosslinking points in the gels) in poorer plasticizers. The exponent characterizing the power-law behavior of the critical gel (G'~G''~ωn), n = 0.75, was insensitive to the plasticizer solubility. The exponent z (= 2.52 ± 0.14), characterizing the equilibrium modulus Ge of the well developed gels (Ge~ez with e =|c - cg |/cg) was also insensitive to the plasticizer solubility. However, the magnitude of the normalized modulus c-1Ge was smaller in poor plasticizers, suggesting some heterogeneity in the gel network structure therein. The other exponent γ characterizing the viscosity η of the sols (η~ eγ) moderately increases from 1.2 to 1.9 with increasing solubility. Comparison of the normalized viscosity and compliance in different plasticizers suggested that the sol structure was heterogeneous and this heterogeneity sensitively increased with decreasing solubility.

Some topics in nonlinear rheology are discussed for polymeric systems: constitutive equation for dilute solutions; strain hardening in elongational flow; chain retraction in entangled systems; stress overshoot of non-entangled systems; entanglement molecular weight.

From a simple calculation considering no thermodynamic requirement of maintaining uniform density, we estimated the effects of spatial confinement on the dielectric relaxation of model block copolymer chains having type-A dipoles. The results were utilized to discuss the relative importancc of these requirement and confinement in the block chain dynamics. For a tail (tethered) chain composed of N segments as well as for loop/bridge chains composed of 2N segments, all confined in a lamella of thickness L=N1/2b (b=segmental step length), the terminal relaxation was moderately faster, its mode distribution was slightly broader, and the dielectric intensity was considerably smaller than those of the same chains in free space. These effects of the spatial confinement were identical for the bridge and loop (either in the knotted or unknotted configuration) and nearly the same also for the tail. The dielectric behavior expected from this calculation was quite different from the behavior of actual type-A blocks. This result strongly suggests that the block chain dynamics is affected much moer significantly by the requirement of maintaining uniform density than by the spatial confinement.

For a wide variety of systems, structures under flow have been investigated with rheo-optical techniques. It is of particular interest and importance to examine the flow effects on structures and dynamics with different techniques. A rheo-dielectric technique, that detects dynamic dielectric responses under flow, is complementary to rheo-optical techniques and provides us with a very useful method of investigating these effects. This article gives a brief review of rheo-dielectric features of some model systems revealed in recent studies to demonstrate the applicability of the rheo-dielectric technique.

Viscoelastic and forced Rayleigh scattering measurements were made on mixtures of PS and PVME over the wide range of temperature and PS molecular weight. The temperature dependence of the tracer diffusion coefficient D of PS in PVME was well described by the shift factor aT obtained from time‐temperature superposition of the dynamic shear modulus data of PVME in bulk. The dependence of D on PS molecular weight was described by the free‐draining Rouse chain model in the low M region where the coil size of the diffusing PS chain is smaller than the mesh size of the PVME entanglement network. In the high M region, on the other hand, D did not decrease in proportion to M−2, being in disagreement with the prediction of the reptation model, but took a constant value nearly equal to the calculated Ds value of the PVME molecule in bulk at the high M end. Two conjectures were proposed for interpretation of the above anomalous diffusion behavior.