Electromechanical deformation of dielectric nematic elastomers accompanied by the rotation of mesogens

Abstract

The electromechanical deformation characteristics of dielectric nematic elastomers (DNEs) are investigated by theoretical modeling and numerical simulation. The results reveal that the electrodeformation of DNEs is caused by both the Maxwell force and rotation of liquid crystal director. The former is the main cause of the electrodeformation of common dielectric elastomers (DEs), while the latter is a unique electrodeformation mechanism of DNEs. Due to the director rotation, DNEs exhibit various modes of electrodeformation, such as elongation, contraction, and shear deformation. Among them, the latter two deformation modes are the unique characteristics of DNEs that are not observed in DEs. The electrodeformation mode of the DNE sample depends on its polymer chain conformation (prolate and oblate) and the rotation direction of the director under electric field (which depends on the positive and negative dielectric properties of the DNE). Therefore, DNEs can be divided into four types according to their chain conformations and dielectric properties. The electrodeformation can be enhanced and optimized by tuning the initial director orientation and/or prestretching. The key to the optimization of electrodeformation is to ensure easy rotation of the director and increase its allowable rotation angle. Further, the phase diagram of DNEs for different material types and director orientations under electromechanical loading is obtained to provide theoretical guidance for the design and optimization of electrodeformation.