Test of tube dilation picture in entangled melts: Self-consistent coarse-graining

Abstract

The current models for the entanglement dynamics of flexible polymers are mostly based on the molecular picture of dynamic tube dilation (DTD). The full-DTD picture, assuming the equivalence of the relaxed portions of the chains and a simple solvent at any time t, fails for binary blends of long and short linear polyisoprene (PI) chains at intermediate t, as revealed from comparison of viscoelastic and dielectric data. In contrast, the partial-DTD picture considering the extent of DTD determined by the constraint release (CR) process gives much better description of the data. The failure of the full-DTD picture and success of partial-DTD picture are noted also for star-branched PI chains. The partial-DTD picture, achieving consistent coarse-graining of the length and time scales, would serve as a good starting point for constructing refined models.