Room-Temperature Zwitterionic Liquid Crystals for Mechanical Actuators

We have developed room-temperature smectic liquid-crystalline (LC) ion conductors by the self-assembly of a zwitterionic mesogenic compound and a series of fluorinated lithium salts. The conductivity of lithium bis(trifluoromethylsulfonyl)imide LC complex reached 4 × 10–3 S cm–1 at ambient conditions. This LC complex sandwiched between two conductive polymer electrodes can be used in low-voltage mechanical actuators with a peak-to-peak bending deflection of ca. 20 mm upon ±1 V, 0.03 Hz excitation

Room-Temperature Zwitterionic Liquid Crystals for Mechanical Actuators

We have developed room-temperature smectic liquid-crystalline (LC) ion conductors by the self-assembly of a zwitterionic mesogenic compound and a series of fluorinated lithium salts. The conductivity of lithium bis(trifluoromethylsulfonyl)imide LC complex reached 4 × 10–3 S cm–1 at ambient conditions. This LC complex sandwiched between two conductive polymer electrodes can be used in low-voltage mechanical actuators with a peak-to-peak bending deflection of ca. 20 mm upon ±1 V, 0.03 Hz excitation

Electroactive Soft Actuators Based on Columnar Ionic Liquid Crystal/Polymer Composite Membrane Electrolytes Forming 3D Continuous Ionic Channels

Here, we report low-voltage-driven fast-response nanostructured columnar ionic liquid crystal/polymer composite actuators that form three-dimensional continuous ion channels. A three-component self-assembly of a zwitterionic rod-like molecule (49.5 wt %), an ionic liquid (27.5 wt %), and poly(vinyl alcohol) (23.0 wt %) provided a free-standing stretchable membrane electrolyte. The dissociated ions can move through a continuous 3D ionophilic matrix surrounding the hydrophobic columns formed by the hexagonally organized rod-mesogens. Three-layer actuators composed of the electrolyte film sandwiched between two conductive polymer film electrodes of doped polythiophene exhibited a bending motion with 0.32% strain and moved 2 mm within 220 ms under 1 V at 0.1 Hz in 70% relative humidity due to the formation of electric double layers at the soft solid electrolyte/electrode interfaces. The bending strain of the columnar nanostructured actuator is comparable to those of polymer iongel actuators and block polymer actuators containing 25–80 wt % of ionic liquids. It is noteworthy that a small number of ions organized into the 3D nanochannels can generate the large bending deformation, which can contribute to reduce the risk of leakage of ions and the production cost. In addition, we have demonstrated a low-voltage-driven deformable mirror actuator that is expected to be applied to optical devices

Electroactive Soft Actuators Based on Columnar Ionic Liquid Crystal/Polymer Composite Membrane Electrolytes Forming 3D Continuous Ionic Channels

Here, we report low-voltage-driven fast-response nanostructured columnar ionic liquid crystal/polymer composite actuators that form three-dimensional continuous ion channels. A three-component self-assembly of a zwitterionic rod-like molecule (49.5 wt %), an ionic liquid (27.5 wt %), and poly(vinyl alcohol) (23.0 wt %) provided a free-standing stretchable membrane electrolyte. The dissociated ions can move through a continuous 3D ionophilic matrix surrounding the hydrophobic columns formed by the hexagonally organized rod-mesogens. Three-layer actuators composed of the electrolyte film sandwiched between two conductive polymer film electrodes of doped polythiophene exhibited a bending motion with 0.32% strain and moved 2 mm within 220 ms under 1 V at 0.1 Hz in 70% relative humidity due to the formation of electric double layers at the soft solid electrolyte/electrode interfaces. The bending strain of the columnar nanostructured actuator is comparable to those of polymer iongel actuators and block polymer actuators containing 25–80 wt % of ionic liquids. It is noteworthy that a small number of ions organized into the 3D nanochannels can generate the large bending deformation, which can contribute to reduce the risk of leakage of ions and the production cost. In addition, we have demonstrated a low-voltage-driven deformable mirror actuator that is expected to be applied to optical devices

Low-Voltage-Driven Actuators Using Photo-Cross-Linked Ionic Columnar Liquid-Crystalline Polymer Films

Liquid-crystalline molecular self-assembly has become an attractive strategy to enhance mass transport and mechanical strength. Herein we report low-voltage-driven actuators based on photo-cross-linked ionic columnar liquid-crystalline polymer films integrating ionic liquids into nanoscale 1D channels. We have unveiled the effect of nanochannels on the actuator performance. The nanostructured actuator exhibits larger deformation and generated force compared with the corresponding amorphous actuator. The concept of nanosegregation consisting of liquid and anisotropic rigid domains will open up a promising pathway for electroactive actuator design

Viologen-Based Redox-Active Ionic Liquid Crystals Forming Columnar Phases

Viologens possessing three alkoxy chains at each terminal self-organize into columnar liquid-crystalline phases through nanophase segregation and electrostatic interactions. These viologens are redox-active and susceptible to two consecutive electrochemical reductions

One-Dimensional Ion Transport in Self-Organized Columnar Ionic Liquids

New fan-shaped ionic liquids forming columnar liquid crystalline phases have been prepared to obtain one-dimensional ion-transporting materials. The ionic liquids consist of two incompatible parts:  an imidazolium-based ionic part as an ion-conducting part and tris(alkyloxy)phenyl parts as insulating parts. Two compounds having octyl and dodecyl chains have been synthesized. Self-assembly of these materials leads to the formation of thermotropic hexagonal columnar liquid crystalline states at room temperature. Anisotropic one-dimensional ionic conductivities have been successfully measured by the cells having comb-shaped gold electrodes. The self-organized columns have been aligned macroscopically in two directions by shearing perpendicular and parallel to the electrodes. The ionic conductivities parallel to the column axis are higher than those perpendicular to the axis. The incorporation of lithium salts in these columnar materials leads to the enhancement of the ionic conductivities and their anisotropy. These materials would be useful for anisotropic transportation of ions at the nanometer level

Viologen-Based Redox-Active Ionic Liquid Crystals Forming Columnar Phases

Viologens possessing three alkoxy chains at each terminal self-organize into columnar liquid-crystalline phases through nanophase segregation and electrostatic interactions. These viologens are redox-active and susceptible to two consecutive electrochemical reductions

Photocured Liquid-Crystalline Polymer Electrolytes with 3D Ion Transport Pathways for Electromechanical Actuators

Self-assembly of ionic molecules into hierarchical ordered structures is a promising route to new types of solid electrolytes with enhanced ion transport. Herein, we report a liquid-crystalline polymer electrolyte membrane that contains three-dimensionally (3D) interconnected ionic pathways. To build this membrane, we used wedge-shaped amphiphilic molecules that have two ionic heads and a lipophilic tail. These molecules were combined with a low content of ionic liquid (5.6 wt %) to form a hexagonal columnar phase, where the self-assembled lipophilic cylinders were surrounded by the ionic shell. Photopolymerization of this phase produced flexible nanostructured films with 3D ionic pathways, which can serve as an electrolyte layer in soft robotic actuators. Ionic transport in the 3D pathways leads to shape memory capability as well as durable bending actuation with a voltage-controllable blocking force. Furthermore, we find a significant enhancement of actuation for the nanostructured electrolyte compared with the corresponding amorphous electrolyte

Electric Field-Assisted Alignment of Self-Assembled Fibers Composed of Hydrogen-Bonded Molecules Having Laterally Fluorinated Mesogens

Aligned fibrous aggregates of amide compounds having laterally fluorinated aromatic mesogens have been successfully obtained by the application of the alternating current electric field (1.0 V/μm, 1 kHz) in dodecylbenzene. In contrast, randomly entangled fibers are formed in the solvent without electric fields. For the analogous compounds without fluorine substituent, no aligned fibrous aggregates have been obtained under the electric fields. The electric field alignment of the fibers should be assisted by the fluorinated rod-shaped mesogens that exhibit negative dielectric anisotropy