Shapeshifting: Reversible Shape Memory in Semicrystalline
Elastomers
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Abstract
We present a general strategy for
enabling reversible shape transformation
in semicrystalline shape memory (SM) materials, which integrates three
different SM behaviors: conventional one-way SM, two-way reversible
SM, and one-way reversible SM. While two-way reversible shape memory
(RSM) is observed upon heating and cooling cycles, the one-way RSM
occurs upon heating only. Shape reversibility is achieved through
partial melting of a crystalline scaffold which secures memory of
a temporary shape by leaving a latent template for recrystallization.
This behavior is neither mechanically nor structurally constrained,
thereby allowing for multiple switching between encoded shapes without
applying any external force, which was demonstrated for different
shapes including hairpin, coil, origami, and a robotic gripper. Fraction
of reversible strain increases with cross-linking density, reaching
a maximum of <i>ca</i>. 70%, and then decreases at higher
cross-linking densities. This behavior has been shown to correlate
with efficiency of securing the temporary shape