English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We employ a first principles, force-level approach to self-consistentlyconstruct the anharmonic tube confinement field for entangled fluids of rigidneedles and for primitive-path (PP) level chains in two limiting situationswhere chain stretching is assumed to either completely relax or remainunrelaxed. The influence of shear and extensional deformation and polymerorientation is determined in a nonlinear elastic limit where dissipativerelaxation processes are intentionally neglected. For needles and PP-levelchains, a Gaussian analysis of transverse polymer dynamical fluctuationspredicts that deformation-induced orientation leads to tube dilation. Incontrast, for deformed polymers in which chain stretch does not relax we findtube compression. For all three systems, a finite maximum transverseentanglement force localizing the polymers in effective tubes is predicted. Theconditions when this entanglement force can be overcome (a force imbalance) byan externally applied force associated with macroscopic deformation can becrisply defined in the nonlinear elastic limit, and the possibility of a"microscopic absolute yielding" event destroying the tube confinement can beanalyzed. For needles and contour-relaxed PP chains, this force imbalance isfound to occur at a stress of order the equilibrium shear modulus and thus astrain of order unity, corresponding to a mechanically fragile entanglementtube field. However, for unrelaxed stretched chains, tube compressionstabilizes transverse polymer confinement, and there appears to be no forceimbalance. These results collectively suggest that the crossover from elasticto irreversible viscous response requires chain retraction to initiatedisentanglement. We qualitatively discuss comparisons with existingphenomenological models for nonlinear startup shear, step strain, and creeprheology experiments.

journal of chemical physics online/the journal of chemical physics/journal of chemical physics

A Force-Level Theory of the Rheology of Entangled Rod and Chain Polymer  Liquids. I. Tube Deformation, Microscopic Yielding and the Nonlinear Elastic  Limit