Shape memory effect and light-induced deformation in Schiff base molecular crystals/PVDF ferroelectric polymer composites

Polyvinylidene difluoride (PVDF)-based polymers have been extensively investigated as a type of electroactive polymer because of their wide applications in flexible sensors, actuators, and transducers. In this work, we demonstrate a new functionality of the PVDF-based polymer-shape memory effect (SME). We show that this effect mainly originates from the ferroelectric-paraelectric phase transition and that shape recovery can be realized at a high speed (<100 ms), superior to most of the existing shape memory polymers. We synthesize modified Schiff base light-sensitive materials and compound them with the polymer to achieve composites exhibiting light-activated SME in the visible light range by exploiting the photothermal effect of the Schiff base compounds. Furthermore, the composites possess light-induced deformation because of the isomerization-induced volume change of the Schiff base molecules under light illumination. To demonstrate the application potential of the multifunctional composites, flexible actuators and robots were designed by combining the thermal-, light-, and electric field-activated SME or deformation. This study not only proposes new multifunctional composites with good application potential, but also presents a new mechanism to design shape memory polymers and expands the functionality of PVDF-based ferroelectric polymers.