Correlation between rearrangements and soft modes in polymer glasses during deformation and recovery

TL;DR

This study investigates how soft vibrational modes in polymer glasses relate to local relaxation events during deformation, aging, and recovery, revealing predictive correlations and their dependence on deformation protocols.

Contribution

It introduces a softness field based on normal modes that predicts rearrangements and analyzes how correlations evolve during aging, deformation, and recovery in polymer glasses.

Findings

Softness predicts up to 70% of rearrangements.

Correlation increases logarithmically during aging and recovery.

Different behaviors observed in uniaxial tension versus shear.

Abstract

We explore the link between soft vibrational modes and local relaxation events in polymer glasses during physical aging, active deformation at constant strain rate, and subsequent recovery. A softness field is constructed out of the superposition of the amplitudes of the lowest energy normal modes, and found to predict up to 70% of the rearrangements. Overlap between softness and rearrangements increases logarithmically during aging and recovery phases as energy barriers rise due to physical aging, while yielding rapidly rejuvenates the overlap to that of a freshly prepared glass. In the strain hardening regime, correlations rise for uniaxial tensile deformation but not for simple shear. These trends can be explained by considering the differing degrees of localization of the soft modes in the two deformation protocols.