Opposite Deformability of Shape-Changing Polymers in Response to a Single Stimulus

Efforts to enhance the capabilities of dynamic systems have been dedicated to the development of “intelligent” soft matter actuators that can undergo logic-based mechanical deformations, enabling adaptive structural morphing and modulation of interactions with local environments. The prevailing soft material building blocks rely primarily on a single transition between bistable states to achieve such functionality. To expand deformation behaviors, one current trend involves superimposing either geometric design or kinetically controlled transient behaviors onto bistable actuators. Complementary to this trend, another promising avenue is to develop a material building block that exhibits two (or more) transitions within itself. This would enable more complex logic-based mechanical deformations, such as subsequent deformations in opposite directions, which could significantly expand the repertoire of encoded mechanical deformations and related functions in a more efficient way, requiring fewer building blocks. However, there are no general chemical design strategies to realize arbitrary, opposite motions in soft material building blocks.<br/>In this work, we report an end-on liquid crystalline elastomer (LCE) that exhibits two-step, opposite mechanical deformations, characterized as a contraction followed by an expansion relative to the starting point along the alignment axis in LCE microstructures under a continuously changing stimulus. By arbitrary manipulation of LCE alignment axis with a magnetic field, we can further extend such opposite deformability to different deformation modes, including tilting and twisting. Moreover, we demonstrate such phase-driven opposite deformability can be readily translated to macroscopic objects and enable the reversible manipulation of the sign of Gaussian curvature in radially aligned films, which was previously challenging to attain.