Stretch-activated morphing enabled by integrated physical-chemical network engineering.

Abstract

Mechanical stimuli-responsive shape transformations, exemplified by mimosa leaves, are widespread in nature, yet remain challenging to realize through facile fabrication in synthetic morphing materials. Herein, we demonstrate stretch-activated shape-morphing enabled by an elastic-plastic bilayer structure assembled via dynamic crosslinking. Through dioxaborolane metathesis, a dynamic, crosslinked polyolefin elastomer (POEV) with elasticity and a co-crosslinked POE/paraffin wax blend (POE/PW-V) with tunable plasticity are prepared. An elastic-plastic mismatched bilayer is then assembled via dioxaborolane metathesis at the interface. Upon stretching and release, the elastic POEV layer attempts to recover, while the plastic POE/PW-V layer resists recovery, inducing curled deformation of the bilayer strips. The localized bilayer design allows for selective activation and region-specific shape transformation under tensile stress, enabling the creation of customizable morphing geometries. Moreover, the low-entropy conformation fixed during stretching spontaneously reverts to a high-entropy state upon heating-induced melting of PW crystals, thereby restoring the original shape. This thermally induced recovery ensures repeatable stretch activation. This work presents a design strategy that integrates physical and chemical network engineering to develop heterogeneously responsive systems, offering promising potential for soft morphing device applications.