Primitive chain network simulations of the creep of entangled polymers

TL;DR

This study uses primitive chain network simulations to explore the creep behavior of entangled polymers, revealing insights into molecular disentanglement and deformation mechanisms under stress-controlled conditions.

Contribution

It introduces modifications to multi-chain sliplink models to simulate creep in entangled polymers, providing new understanding of molecular dynamics during creep.

Findings

Qualitative agreement with experimental creep data

Disentanglement is milder in stress-controlled mode

Molecular tumbling is disrupted at flow start

Abstract

Although the behavior of entangled polymers in startup shear flows with constant shear rates has been thoroughly investigated, the response under creep has not been frequently considered. In this study, primitive chain network simulations, based on a multi-chain sliplink model, are modified so as to describe creep experiments. Creep simulations are compared to a literature dataset of an entangled polybutadiene solution, and qualitative agreement is found in the nonlinear range, i.e., under large stresses. Simulations allow one to extract details of the transient molecular motion, and results suggest that the deformation-induced disentanglement is relatively mild in the stress-controlled mode as compared to the rate-controlled one, because coherent molecular tumbling at the start of flow is disrupted.