Chain level insights into tensile-compressive asymmetry in glassy and semicrystalline polymers

TL;DR

This study uses molecular dynamics simulations to analyze chain-level behaviors in polymers under tensile and compressive stresses, revealing distinct organizational patterns and deformation mechanisms that depend on chain length.

Contribution

It provides new insights into the molecular-level differences in polymer deformation under tension and compression, highlighting the role of chain length and organization.

Findings

Polymers align along tensile axis with nematic order.

Under compression, polymers form anti-nematic order in a plane.

Unfolding is greater under tension and deformation is less affine.

Abstract

Using molecular dynamics simulations, we provide chain-level insights into the dissimilarities in rearrangements of polymers under uniaxial tensile and compressive deformation in glassy and semicrystalline samples of varying chain lengths. The organization of polymers under tension and compression is distinctively different. The chains align themselves along the tensile axis leading to a net global nematic ordering of their bonds and end-to-end vectors whereas under compression, the polymers arrange themselves in a plane perpendicular to the compressive axis resulting in emergence of an anti-nematic ordering of the bonds and the chain end-to-end vectors. Moreover, the degree of polymers unfolding is greater under tension and they deform less affinely when compared to chains under compression. The difference between the two responses strongly depends on the chain length and is the largest at intermediate chain lengths.