Surface energy of strained amorphous solids

TL;DR

This study investigates how surface energies of amorphous solids like glasses and elastomers depend on strain, revealing strain dependence in glasses but not in incompressible elastomers, through contact angle measurements.

Contribution

It provides the first direct measurements demonstrating strain-dependent surface energies in amorphous glasses and confirms the absence of such dependence in elastomers.

Findings

Surface energy of polymeric glasses depends on strain.

Incompressible elastomers show no strain dependence.

Contact angle measurements effectively reveal surface energy variations.

Abstract

Surface stress and surface energy are fundamental quantities which characterize the interface between two materials. Although these quantities are identical for interfaces involving only fluids, the Shuttleworth effect demonstrates that this is not the case for most interfaces involving solids, since their surface energies change with strain. Crystalline materials are known to have strain dependent surface energies, but in amorphous materials, such as polymeric glasses and elastomers, the strain dependence is debated due to a dearth of direct measurements. Here, we utilize contact angle measurements on strained glassy and elastomeric solids to address this matter. We show conclusively that interfaces involving polymeric glasses exhibit strain dependent surface energies, and give strong evidence for the absence of such a dependence for incompressible elastomers. The results provide fundamental insight into our understanding of the interfaces of amorphous solids and their interaction with contacting liquids.