Rheology of a Supercooled Polymer Melt

TL;DR

This study uses molecular dynamics simulations to explore the rheological behavior of supercooled polymer melts, revealing stress relaxation patterns, shear-thinning, and chain elongation under shear conditions.

Contribution

It provides new insights into the stress relaxation and flow behavior of supercooled polymer melts through detailed simulation analysis.

Findings

Stress relaxation follows a stretched exponential then Rouse function.

Transient stress growth is linear at low strain and saturates.

Strong shear-thinning and chain elongation occur at small shear.

Abstract

Molecular dynamics simulations are performed for a polymer melt composed of short chains in quiescent and sheared conditions. The stress relaxation function $G(t)$ exhibits a stretched exponential form in a relatively early stage and ultimately follows the Rouse function in quiescent supercooled state. Transient stress evolution after application of shear obeys the linear growth $\int_0^t dt'G(t')$ for strain less than 0.1 and then saturates into a non-Newtonian viscosity. In steady states, strong shear-thinning and elongation of chains into ellipsoidal shapes are found at extremely small shear. A glassy component of the stress is much enhanced in these examples.