Mechanically Tough Micellar Cubic Liquid‐Crystalline Polymer Electrolytes for Electromechanical Actuators

Abstract

This study presents a novel micellar cubic ionic liquid‐crystalline polymer electrolyte, featuring an alignment‐free spherical structure with unimpeded 3D ionic pathways, aimed at enhancing the performance of an ionic electroactive polymer actuator. The development involved creating a mechanically tough and high ion‐conductive cubic polymer film through the self‐assembly of a wedge‐shaped vinyl imidazolium salt and an imidazolium ionic liquid, followed by in situ photopolymerization. The 300 µm‐thick‐trilayer films, consisting of the cubic polymer electrolyte sandwiched between poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) electrodes, exhibit remarkable capabilities. These include bearing substantial loads of 4 g with a high blocking force under a DC voltage of 2 V, achieving a high bending strain of 0.63% under a low input voltage (±2 V, 0.1 Hz), and boasting a maximum response frequency of 70 Hz. These properties position the material for potential applications in soft robots and tactile sensing devices.

Ionic Liquid Crystal–Polymer Composite Electromechanical Actuators: Design of Two-Dimensional Molecular Assemblies for Efficient Ion Transport and Effect of Electrodes on Actuator Performance

“…Nuclear magnetic resonance (NMR) spectra were acquired by using a JEOL ECZ 400S spectrometer. Chemical shifts (δ) are reported in ppm with respect to internal or external standards for CDCl 3 solutions: tetramethylsilane (δ = 0 ppm) for 1 H NMR (400 MHz) and CHCl 3 (δ = 77.0 ppm) for 13 C NMR (100 MHz). Elemental analysis for C, H, and N was conducted using an ELEMENTAR vario EL cube.…”

“…1 H NMR (400 MHz, CDCl 3 ): δ = 7.10 (dt, J = 9.5, 2.4 Hz, 2H; ArH), 6.80 (dt, J = 9.3, 2.5 Hz, 2H; ArH), 4.05 (q, J = 6.7 Hz, 2H; CH 2 ), 3.95−3.89 (m, 2H; CH 2 ), 3.75 (dd, J = 14.9, 3.9 Hz, 6H, CH 3 ), 2.39 (tt, J = 12.1, 3.1 Hz, 1H; CH), 1.86−1.68 (m, 8H; CH 2 ), 1.53−1.17 (m, 15H, CH, CH 2 ), 1.02 (ddd, J = 24.0, 12.8, 3.2 Hz, 2H; CH 2 ), 0.90 (q, J = 7.3 Hz, 3H, CH 3 ). 13 Preparation of Ionic Liquid Crystals. Mesogenic phosphate (POMe or POEt) was mixed with an acetone solution of either BMImPF 6 or LiTFSI at molar ratios of 9:1, 8:2, 7:3, 6:4, and 5:5.…”

“…The pursuit of efficient ion transport pathways within organic and inorganic thin films has garnered significant attention as a strategic approach to improving energy efficiency in batteries, energy harvesting, actuators, water treatments, and more. − In the realm of energy device technologies, various nanostructured polymers have been recognized for their ability to provide high ionic conductivity and mechanical robustness. This category encompasses block ionomers, ionic covalent organic frameworks, supramolecular polymers, and ionic liquid crystalline (LC) polymers. − Among them, liquid crystals stand out as particularly promising due to their large-area orientation achievable through diverse external stimuli such as mechanical shear, light, and electric and magnetic fields. − Nanostructured LC polymers featuring continuous ion-conductive channel networks have been prepared by photopolymerization of thermotropic liquid crystals tethering oligo­(ethylene oxide) chains complexed with lithium salts and lyotropic liquid crystals incorporating liquid electrolytes such as ionic liquids and cyclic carbonates . However, the development of flexible and mechanically durable LC polymer membranes for soft actuator applications is still in its early stage.…”