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

Abstract

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.

Ionic electroactive PEDOT:PSS/liquid-crystalline polymer electrolyte actuators: photopolymerization of zwitterionic columnar liquid crystals complexed with a protic ionic liquid

“…A free-standing film electrode was prepared by casting an aqueous solution of PEDOT:PSS containing 6 wt% ethylene glycol. 48…”

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

“…In sharp contrast to our recent work on the 3D ion-conductive columnar liquid crystal/polymer composite membranes, the present approach that employs supramolecular columnar LC self-assembly of the amphiphilic monomers and the IL and in situ photopolymerization has the benefit of tuning the physicochemical and electrochemical properties by changing the mixing ratios and the orientability of columns as well as easier fabrication of membranes without a solvent evaporation process.…”

“…Recent successes in iEAP actuators were based on the use of nanostructured polymer electrolytes containing an ionic liquid ( IL ). Self-assembly of block copolymers, ,− liquid crystals, , and covalent organic frameworks forms hierarchically ordered ionic nanochannels, which accelerates the ionic transport. However, most high-performance actuators based on these advanced electrolytes contain more than 50 wt % IL , ,− which increases the bending strain and reduces the response time but lowers the mechanical modulus.…”

“…One of the promising approaches to achieving continuous ion transport in nanostructured soft materials is the use of hexagonal ordering of nanosegregated columns consisting of ionophobic cylinders surrounded by ionic shells, in which ions could jump from one column to the other, even if the columns are randomly oriented. Recently, we used this concept and developed fast-response LC actuators based on columnar ionic liquid crystal/polymer composite membrane electrolytes forming three-dimensionally (3D) continuous ion pathways . Columnar assembled structures were designed by noncovalent supramolecular self-assembly of a nonpolymerizable rod-shaped zwitterionic mesogenic molecule, an IL , and poly­(vinyl alcohol).…”

“…Recently, we used this concept and developed fast-response LC actuators based on columnar ionic liquid crystal/polymer composite membrane electrolytes forming three-dimensionally (3D) continuous ion pathways. 22 Columnar assembled structures were designed by noncovalent supramolecular self-assembly of a nonpolymerizable rodshaped zwitterionic mesogenic molecule, an IL, and poly(vinyl alcohol). These actuators showed a high bending strain of 0.3% under 1 V at 0.1 Hz in high humidity environments above 60% RH.…”