Module-Assembled Elastomer Showing Large Strain Stiffening Capability and High Stretchability

Elastomers are indispensable materials due to their flexible, stretchable, and elastic nature. However, the polymer network structure constituting an elastomer is generally inhomogeneous, limiting the performance of the material. Here, a highly stretchable elastomer with unprecedented strain-stiffening capability is developed based on a highly homogeneous network structure enabled by a module assembly strategy. The elastomer is synthesized by efficient end-linking of a star-shaped aliphatic polyester precursor with a narrow molecular-weight distribution. The resulting product shows high strength (approximate to 26 MPa) and remarkable stretchability (stretch ratio at break approximate to 1900%), as well as good fatigue resistance and notch insensitivity. Moreover, it shows extraordinary strain-stiffening capability (>2000-fold increase in the apparent stiffness) that exceeds the performance of any existing soft material. These unique properties are due to strain-induced ordering of the polymer chains in a uniformly stretched network, as revealed by in situ X-ray scattering analyses. The utility of this great strain-stiffening capability is demonstrated by realizing a simple variable stiffness actuator for soft robotics.

Automated summary

A highly stretchable elastomer with unprecedented strain-stiffening capability has been developed based on a highly homogeneous network structure enabled by a module assembly strategy. This elastomer, synthesized by efficient end-linking of a star-shaped aliphatic polyester precursor, exhibits high strength, remarkable stretchability, good fatigue resistance, and notch insensitivity. It also shows extraordinary strain-stiffening capability that exceeds the performance of any existing soft material, due to strain-induced ordering of the polymer chains in a uniformly stretched network.