Perspectives on the viscoelasticity and flow behavior of entangled linear and branched polymers

TL;DR

This paper reviews recent advances in understanding the viscoelasticity and flow behavior of entangled linear and branched polymers, highlighting experimental, theoretical, and modeling perspectives, and identifying future research directions.

Contribution

It critically assesses the tube model's effectiveness and discusses emerging challenges and alternative approaches in the rheology of entangled polymers, especially branched types.

Findings

Shear banding instabilities observed in experiments

Multiple stress overshoots in transient shear

Enhanced steady-state elongational viscosity in solutions

Abstract

We briefly review the recent advances in the rheology of entangled polymers and identify emerging research trends and outstanding challenges, especially with respect to branched polymers. Emphasis is placed on the role of well-characterized model systems, as well as the synergy of synthesis-characterization, rheometry and modeling/simulations. The theoretical framework for understanding the observed linear and nonlinear rheological phenomena is the tube model which is critically assessed in view of its successes and shortcomings, whereas alternative approaches are briefly discussed. Finally, intriguing experimental findings and controversial issues that merit consistent explanation, such as shear banding instabilities, multiple stress overshoots in transient simple shear and enhanced steady-state elongational viscosity in polymer solutions, are discussed, whereas future directions such as branch point dynamics and anisotropic monomeric friction are outlined.