Topological origin of strain induced damage of multi-network elastomers by bond breaking

TL;DR

This study reveals that strain-induced damage in multi-network elastomers is governed by topological changes in the polymer network, specifically the evolution of the shortest path length between cross-links, linking molecular structure to mechanical behavior.

Contribution

It introduces a topological framework to predict bond-breaking patterns in elastomers, advancing understanding of damage evolution under strain.

Findings

Bond-breaking events are controlled by the evolution of the shortest path length.

The shortest path length evolution is anisotropic and hysteretic with strain.

The study links molecular topology to macroscopic mechanical properties.

Abstract

Elastomers that can sustain large reversible strain are essential components for stretchable electronics. The stretchability and mechanical robustness of unfilled elastomers can be enhanced by introducing easier-to-break cross-links, e.g. through the multi-network structure, which also causes stress-strain hysteresis indicating strain-induced damage. However, it remains unclear whether cross-link breakage follows a predictable pattern that can be used to understand the damage evolution with strain. Using coarse-grained molecular dynamics and topology analyses of the polymer network, we find that bond-breaking events are controlled by the evolution of the global shortest path length between well-separated cross-links, which is both anisotropic and hysteretic with strain. These findings establish an explicit connection between the molecular structure and the macroscopic mechanical behavior of elastomers, thereby providing guidelines for designing mechanically robust soft materials.