Multifunctional Ionene Liquid Crystal Elastomers

Incorporating ionic species into the backbone of liquid crystalline elastomers offers a template for tailoring thermomechanical and electromechanical properties. Thermotropic ionene liquid crystalline elastomers (iLCEs) containing imidazolium-based cationic groups are capable of work-dense (∼14 J/kg), large-strain (>30%) actuation at modest temperatures (∼40 °C). Furthermore, the constitutive behavior of iLCE is modulated by ionic liquid (IL) dopants, which magnify the large strain deformability (>600%), modulate pressure-sensitive adhesion, and enable strain sensing over ∼100% strain at a constant stress defined by its soft elastic plateau. The nascent electronic conductivity of iLCE is sensitive to temperature, which unlocks a route for sustaining actuation cycles by gating the actinic stimulus using materially embodied sensing. iLCEs are also capable of athermal electromechanical actuation. Ion migration at low voltages (<3 V) in iLCEs with anisotropic molecular order produces bending strains that compete favorably against traditional ionic actuators. This responsiveness is modulated by the structure and alignment of the nematic axis with respect to the applied electrical fields. The ability to modulate the electromechanical coupling in iLCEs on top of the thermomechanical properties traditionally derived from liquid crystallinity enables a motif for assimilating an array of multifunctional properties.