High Ionic Liquid Content Polymeric Gel Membranes: Preparation and Performance

Development of an ion gel-based CO2 separation membrane composed of Pebax 1657 and a CO2-philic ionic liquid

A tough ion gel membrane containing a CO2-philic ionic liquid, 1-ethyl-3-methylimidazolium tricyanomethanide ([Emim][C(CN)3]), was developed, and its CO2 permeation properties were evaluated under humid conditions at elevated temperatures. Pebax 1657, which is a diblock copolymer composed of a polyamide block and a polyethylene oxide block, was used as the gel network of the ion gel membrane to prepare a tough ion gel with good ionic liquid-holding properties. The polyamide block formed a semicrystalline structure in [Emim][C(CN)3] to toughen the ion gel membrane via an energy dissipation mechanism. The polyethylene oxide block exhibited good compatibility with [Emim][C(CN)3] and contributed to the retention of the ionic liquid in the ion gel. The developed ion gel membrane showed a good CO2 separation performance of 1677 barrer CO2 permeability and 37 CO2/N2 permselectivity under humid conditions of 75% relative humidity at an elevated temperature of 50 °C, which corresponds to an exhaust gas from a coal-fired power plant.

Mechanically and Thermally Robust Gel Electrolytes Built from A Charged Double Helical Polymer

Polymer electrolytes have received tremendous interest in the development of solid-state batteries, but often fall short in one or more key properties required for practical applications. Herein, a rigid gel polymer electrolyte prepared by immobilizing a liquid mixture of a lithium salt and poly(ethylene glycol) dimethyl ether with only 8 wt% poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT) is reported. The high charge density and rigid double helical structure of PBDT lead to formation of a nanofibrillar structure that endows this electrolyte with stronger mechanical properties, wider temperature window, and higher battery rate capability compared to all other poly(ethylene oxide) (PEO)-based electrolytes. The ion transport mechanism in this rigid polymer electrolyte is systematically studied using multiple complementary techniques. Li/LiFePO4 cells show excellent capacity retention over long-term cycling, with thermal cycling reversibility between ambient temperature and elevated temperatures, demonstrating compelling potential for solid-state batteries targeting fast charging at high temperatures and slower discharging at ambient temperature.

Poly(ethylene oxide)-Based Copolymer-IL Composite Membranes for CO2 Separation

Poly(ethylene oxide) (PEO)-based copolymers are at the forefront of advanced membrane materials for selective CO₂ separation. In this work, free-standing composite membranes were prepared by blending imidazolium-based ionic liquids (ILs) having different structural characteristics with a PEO-based copolymer previously developed by our group, targeting CO₂ permeability improvement and effective CO₂/gas separation. The effect of IL loading (30 and 40 wt%), alkyl chain length of the imidazolium cation (ethyl- and hexyl- chain) and the nature of the anion (TFSI^-, C(CN)₃^-) on physicochemical and gas transport properties were studied. Among all composite membranes, PEO-based copolymer with 40 wt% IL3-[HMIM][TFSI] containing the longer alkyl chain of the cation and TFSI^- as the anion exhibited the highest CO₂ permeability of 46.1 Barrer and ideal CO₂/H₂ and CO₂/CH₄ selectivities of 5.6 and 39.0, respectively, at 30 °C. In addition, almost all composite membranes surpassed the upper bound limit for CO₂/H₂ separation. The above membrane showed the highest water vapor permeability value of 50,000 Barrer under both wet and dry conditions and a corresponding H₂O/CO₂ ideal selectivity value of 1080; values that are comparable with those reported for other highly water-selective PEO-based polymers. These results suggest the potential application of this membrane in hydrogen purification and dehydration of CO₂ gas streams.

Compressive-Strain-Facilitated Fast Oxygen Migration with Reversible Topotactic Transformation in La0.5Sr0.5CoOx via All-Solid-State Electrolyte Gating

Modifying the crystal structure and corresponding functional properties of complex oxides by regulating their oxygen content has promising applications in energy conversion and chemical looping, where controlling oxygen migration plays an important role. Therefore, finding an efficacious and feasible method to facilitate oxygen migration has become a critical requirement for practical applications. Here, we report a compressive-strain-facilitated oxygen migration with reversible topotactic phase transformation (RTPT) in La_0.5Sr_0.5CoO_x films based on all-solid-state electrolyte gating modulation. With the lattice strain changing from tensile to compressive strain, significant reductions in modulation duration (∼72%) and threshold voltage (∼70%) for the RTPT were observed, indicating great promotion of RTPT by compressive strain. Density functional theory calculations verify that such compressive-strain-facilitated efficient RTPT comes from significant reduction of the oxygen migration barrier in compressive-strained films. Further, ac-STEM, EELS, and sXAS investigations reveal that varying strain from tensile to compressive enhances the Co 3d band filling, thereby suppressing the Co-O hybrid bond in oxygen vacancy channels, elucidating the micro-origin of such compressive-strain-facilitated oxygen migration. Our work suggests that controlling electronic orbital occupation of Co ions in oxygen vacancy channels may help facilitate oxygen migration, providing valuable insights and practical guidance for achieving highly efficient oxygen-migration-related chemical looping and energy conversion with complex oxides.

Water Washable and Flexible Light-Emitting Fibers Based on Electrochemiluminescent Gels

Herein, a new concept of device architecture to fabricate fibrous light-emitting devices is demonstrated based on an electrochemiluminescence (ECL) material for an electronic textile system. A unique feature of this work is that instead of conventional semiconductor materials, such as organics, perovskites, and quantum dots for fibrous light emitting devices, a solid-state ECL electrolyte gel is employed as a light-emitting layer. The solid-state ECL gel is prepared from a precursor solution composed of matrix polymer, ionic liquid, and ECL luminophore. From this, we successfully realize light-emitting fibers through a simple and cost-effective single-step dip-coating method in ambient air, without complicated multistep vacuum processes. The resulting fiber devices reliably operated under applied AC bias of ±2.5 V and showed luminance of 47 cd m^-2. More importantly, the light-emitting fibers exhibited outstanding water resistance without any passivation layers, owing to the water immiscible and hydrophobic nature of the ECL gel. In addition, because of their simple structure, the fiber devices can be easily deformed and woven together with commercial knitwear by hand. Therefore, these results suggest a promising strategy for the development of practical fiber displays and contribute to progress in electronic textile technology.

Emerging iongel materials towards applications in energy and bioelectronics

In the past two decades, ionic liquids (ILs) have blossomed as versatile task-specific materials with a unique combination of properties, which can be beneficial for a plethora of different applications. The additional need of incorporating ILs into solid devices led to the development of a new class of ionic soft-solid materials, named here iongels. Nowadays, iongels cover a wide range of materials mostly composed of an IL component immobilized within different matrices such as polymers, inorganic networks, biopolymers or inorganic nanoparticles. This review aims at presenting an integrated perspective on the recent progress and advances in this emerging type of material. We provide an analysis of the main families of iongels and highlight the emerging types of these ionic soft materials offering additional properties, such as thermoresponsiveness, self-healing, mixed ionic/electronic properties, and (photo)luminescence, among others. Next, recent trends in additive manufacturing (3D printing) of iongels are presented. Finally, their new applications in the areas of energy, gas separation and (bio)electronics are detailed and discussed in terms of performance, underpinning it to the structural features and processing of iongel materials.

High-Performance Room Temperature Lithium-Ion Battery Solid Polymer Electrolytes Based on Poly(vinylidene fluoride-co-hexafluoropropylene) Combining Ionic Liquid and Zeolite

The demand for more efficient energy storage devices has led to the exponential growth of lithium-ion batteries. To overcome the limitations of these systems in terms of safety and to reduce environmental impact, solid-state technology emerges as a suitable approach. This work reports on a three-component solid polymer electrolyte system based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), the ionic liquid 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]), and clinoptilolite zeolite (CPT). The influences of the preparation method and of the dopants on the electrolyte stability, ionic conductivity, and battery performance were studied. The developed electrolytes show an improved room temperature ionic conductivity (1.9 × 10^-4 S cm^-1), thermal stability (up to 300 °C), and mechanical stability. The corresponding batteries exhibit an outstanding room temperature performance of 160.3 mAh g^-1 at a C/15-rate, with a capacity retention of 76% after 50 cycles. These results represent a step forward in a promising technology aiming the widespread implementation of solid-state batteries.

Effects of Ionic Liquid Nanoconfinement on the CO2/CH4 Separation in Poly(vinylidene fluoride)/1-Ethyl-3-methylimidazolium Thiocyanate Membranes

A combined experimental and molecular dynamics (MD) simulation approach was used to investigate the effects of the nanoconfinement of a highly CO₂/CH₄-selective ionic liquid (IL), 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]), in porous poly(vinylidene fluoride) (PVDF) matrices on the gas separation performance of the resulting membranes. The observed experimental CO₂/CH₄ permselectivity increased by about 46% when the nominal pore diameter in PVDF, which is a measure of nanoconfinement, decreased from 450 to 100 nm, thus demonstrating nanoconfinement improvements of gas separation. MD simulations corroborated these experimental observations and indicated a suppression in the sorption of CH₄ by [EMIM][SCN] when the IL nanoconfinement length decreased within the nonpolar PVDF surfaces. This is consistent with the experimental observation that the CH₄ permeance through the IL confined in nonpolar PVDF is significantly less than the CH₄ permeance through the IL confined in a water-wetting polar formulation of PVDF. The potential of mean force calculations further indicated that CO₂ has more affinity to the nonpolar PVDF surface than CH₄. Also, a charge/density distribution analysis of the IL in the PVDF-confined region revealed a layering of the IL into [EMIM]- and [SCN]-rich regions, where CH₄ was preferentially distributed in the former and CO₂ in the latter. These molecular insights into the nanoconfinement-driven mechanisms in polymer/IL membranes provide a framework for a better molecular design of such membranes for critical gas separation and CO₂ capture applications.

Density functional theory-based analyses on selective gas separation by β-PVDF-supported ionic liquid membranes

Finding proper candidates for polymer-supported ionic liquid (IL)-based gas separating membranes is a challenge. The current article elucidates the quantum chemical perspective of the selective gas adsorption efficiency, from a mixture of CO₂, CO, CH₄, and H₂, of α- and β-polyvinylidene fluoride (PVDF)-supported imidazolium- and pyridinium-based six ionic liquid membranes. Although IL-based membrane efficiency mainly depends on the gas solubility of ILs, IL/support binding and gas adsorption on the support material are also studied to describe the overall gas adsorption properties of the PVDF/IL complexes. β-PVDF exhibits better binding with the ILs, and better gas affinity, thus, qualified as a more suitable membrane component as compared to α-PVDF. Dispersion-corrected density functional calculations are performed to provide a detailed insight into the energetic interactions, nonbonding intermolecular interactions based on symmetry adapted perturbation theory (SAPT), natural bond orbitals (NBO), Bader's quantum theory of atoms in molecules (QTAIM), reduced density gradient (RDG), frontier orbital interactions, density of states (DOS), and thermochemical analyses of the gas-adsorbed systems. Gas molecules interact with the membrane components through weak hydrogen bonds and exhibit low interaction energies, indicating physisorption of the gases. Gas adsorption energies are more negative than the mutual interaction energies of the gas molecules, ensuring effective gas adsorption by the membrane components. All the β-PVDF/IL systems have shown the highest and lowest affinity for CO2 and H2, respectively, leading to effective separation of CO₂ and H₂ from the other gases.

Recent Advances of Pervaporation Separation in DMF/H2O Solutions: A Review

N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% spent liquors (mass fraction) that are difficult to recycle with distillation. From the point of view of energy-efficiency and environment-friendliness, an emergent separation technology, pervaporation, is broadly applied in separation of azeotropic mixtures and organic–organic mixtures, dehydration of aqueous–organic mixtures and removal of trace volatile organic compounds from aqueous solutions. Since the advances in membrane technologies to separate N,N-dimethylformamide solutions have been rarely reviewed before, hence this review mainly discusses the research progress about various membranes in separating N,N-dimethylformamide aqueous solutions. The current state of available membranes in industry and academia, and their potential advantages, limitations and applications are also reviewed.

Development of Novel Polyamide-Imide/DES Composites and Their Application for Pervaporation and Gas Separation

Novel polymer composites based on polyamide–imide Torlon and deep eutectic solvent (DES) were fabricated and adapted for separation processes. DES composed of zinc chloride and acetamide in a ratio of 1:3 M was first chosen as a Torlon-modifier due to the possibility of creating composites with a uniform filling of the DES through the formation of hydrogen bonds. The structure of the membranes was investigated by scanning electron microscopy and X-ray diffraction analysis; thermal stability was determined by thermogravimetric analysis and mass spectrometry. The surface of the composites was studied by determining the contact angles and calculating the surface tension. The transport properties were investigated by such membrane methods as pervaporation and gas separation. It was found that the inclusion of DES in the polymer matrix leads to a significant change in the structure and surface character of composites. It was also shown that DES plays the role of a plasticizer and increases the separation performance in the separation of liquids and gases. Torlon/DES composites with a small amount of modifier were effective in alcohol dehydration, and were permeable predominantly to water impurities in isopropanol. Torlon/DES-5 demonstrates high selectivity in the gas separation of O₂/N₂ mixture.

A Review on Ionic Liquid Gas Separation Membranes

Ionic liquids have attracted the attention of the industry and research community as versatile solvents with unique properties, such as ionic conductivity, low volatility, high solubility of gases and vapors, thermal stability, and the possibility to combine anions and cations to yield an almost endless list of different structures. These features open perspectives for numerous applications, such as the reaction medium for chemical synthesis, electrolytes for batteries, solvent for gas sorption processes, and also membranes for gas separation. In the search for better-performing membrane materials and membranes for gas and vapor separation, ionic liquids have been investigated extensively in the last decade and a half. This review gives a complete overview of the main developments in the field of ionic liquid membranes since their first introduction. It covers all different materials, membrane types, their preparation, pure and mixed gas transport properties, and examples of potential gas separation applications. Special systems will also be discussed, including facilitated transport membranes and mixed matrix membranes. The main strengths and weaknesses of the different membrane types will be discussed, subdividing them into supported ionic liquid membranes (SILMs), poly(ionic liquids) or polymerized ionic liquids (PILs), polymer/ionic liquid blends (physically or chemically cross-linked 'ion-gels'), and PIL/IL blends. Since membrane processes are advancing as an energy-efficient alternative to traditional separation processes, having shown promising results for complex new separation challenges like carbon capture as well, they may be the key to developing a more sustainable future society. In this light, this review presents the state-of-the-art of ionic liquid membranes, to analyze their potential in the gas separation processes of the future.

Organic Ionic Plastic Crystal-Based Composite Membranes for Light Gas Separation: The Impact of Varying Ion Type and Casting Method

The promise of organic ionic plastic crystals (OIPCs) for development of a novel type of gas separation membrane with competitive gas selectivity for CO₂ /N₂ was recently demonstrated. This work aimed to design more selective membranes by investigating a different type of OIPC and a new membrane preparation method. Two different OIPCs were solvent-cast or co-cast with poly(vinylidene difluoride) (PVDF), and their gas transport properties were compared. The first OIPC, methyl(diethyl)isobutylphosphonium hexafluorophosphate ([P_122i4 ][PF₆ ]), was previously studied using the co-cast method, and this was used as a benchmark. The second, N-methyl-N-ethylpyrrolidinium bis(fluorosulfonyl)imide ([C₂ mpyr][FSI]), was investigated for the first time for gas separation applications, achieving high selectivities (α CO 2 / N 2 >40). The thermophysical properties of the composites indicated that the co-casting method is a good way to fabricate solid, mechanically stable and durable membranes. Additionally, the enhanced molecular interactions indicated in OIPC/PVDF co-cast composites point to a new approach for synthesis of other highly selective OIPC-based membranes.

Key Applications and Potential Limitations of Ionic Liquid Membranes in the Gas Separation Process of CO2, CH4, N2, H2 or Mixtures of These Gases from Various Gas Streams

Heightened levels of carbon dioxide (CO₂) and other greenhouse gases (GHGs) have prompted research into techniques for their capture and separation, including membrane separation, chemical looping, and cryogenic distillation. Ionic liquids, due to their negligible vapour pressure, thermal stability, and broad electrochemical stability have expanded their application in gas separations. This work provides an overview of the recent developments and applications of ionic liquid membranes (ILMs) for gas separation by focusing on the separation of carbon dioxide (CO₂), methane (CH₄), nitrogen (N₂), hydrogen (H₂)_, or mixtures of these gases from various gas streams. The three general types of ILMs, such as supported ionic liquid membranes (SILMs), ionic liquid polymeric membranes (ILPMs), and ionic liquid mixed-matrix membranes (ILMMMs) for the separation of various mixed gas systems, are discussed in detail. Furthermore, issues, challenges, computational studies and future perspectives for ILMs are also considered. The results of the analysis show that SILMs, ILPMs, and the ILMMs are very promising membranes that have great potential in gas separation processes. They offer a wide range of permeabilities and selectivities for CO₂, CH₄, N₂, H₂ or mixtures of these gases. In addition, a comparison was made based on the selectivity and permeability of SILMs, ILPMs, and ILMMMs for CO₂/CH₄ separation based on a Robeson’s upper bound curves.

Protic Imidazolium Cation-Based Ionic Liquids Show Unexpected Interfacial Properties

Virtually, every investigation and application of ionic liquids (ILs) involves gas-liquid, liquid-liquid, and liquid-solid interactions. Therefore, understanding the behavior of ILs at those interfaces is critical. In this work, we studied the interfacial properties of protic and aprotic ILs with N-alkylimidazolium and 1-alkyl-3-methylimidazolium as cations and bis(trifluoromethylsulfonyl)imide, methanesulfonate, and trifluoromethanesulfonate as anions. The surface tension of these ILs is measured with the pendant drop method in a temperature range of 293.15-343.15 K and at atmospheric pressure. The contact angle measurements are performed at 293.15 K on three solid substrates: polytetrafluoroethylene, glassy carbon, and platinum. Dispersive and nondispersive components of the IL surface energy are determined from the experimental data using Fowkes theory. The most interesting result is that the protic ILs have lower surface tension and smaller contact angles than the equivalent aprotic ILs, despite the presence of high charge density on the proton associated with one of the nitrogens of the cation. Higher charge density on the anion results in a higher surface tension, and decreasing surface tension and contact angles are observed for increasing alkyl chain length on the cation.

Tailoring the Thermal and Mechanical Properties of PolyActiveTM Poly(Ether-Ester) Multiblock Copolymers Via Blending with CO2-Phylic Ionic Liquid

The last decade has seen an exponential increase in the number of studies focused on novel applications for ionic liquids (ILs). Blends of polymers with ILs have been proposed for use in fuel cells, batteries, gas separation membranes, packaging, etc., each requiring a set of specific physico-chemical properties. In this work, blends of four grades of the poly(ether-ester) multiblock copolymer PolyActive™ with different concentrations of the CO₂-philic 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf₂N] were prepared in the form of dense films by a solution casting and solvent evaporation method, in view of their potential use as gas separation membranes for CO₂ capture. Depending on the polymer structure, the material properties could be tailored over a wide range by means of the IL content. All samples were dry-feeling, highly elastic self-standing dense films. The microstructure of the blends was studied by scanning electron microscopy with a backscattering detector, able to observe anisotropy in the sample, while a special topographic analysis mode allowed the visualization of surface roughness. Samples with the longest poly(ethylene oxide terephthalate) (PEOT) blocks were significantly more anisotropic than those with shorter blocks, and this heterogeneity increased with increasing IL content. DSC analysis revealed a significant decrease in the melting enthalpy and melting temperature of the crystalline PEOT domains with increasing IL content, forming an amorphous phase with T_g ≈ −50 °C, whereas the polybutylene terephthalate (PBT) phase was hardly affected. This indicates better compatibility of the IL with the polyether phase than the polyester phase. Young’s modulus was highest and most IL-dependent for the sample with the highest PEOT content and PEOT block length, due to its high crystallinity. Similarly, the sample with short PEOT blocks and high PBT content also showed a high modulus and tensile strength, but much lower maximum elongation. This study provides a detailed discussion on the correlation between the morphological, thermal, and mechanical properties of these PolyActive™/[BMIM][Tf₂N] blends.

Thermostable Ion Gels for High-Temperature Operation of Electrolyte-Gated Transistors

High-temperature durability is critical for application of organic materials in electronic devices that operate in harsh environments. In this work, thermostable physically cross-linked polymer electrolytes, or thermostable physical ion gels, were successfully developed using crystallization-induced phase separation of semicrystalline polyamides (PAs) in an ionic liquid (IL). In these ion gels, phase-separated PA crystals act as network junctions and enable the ion gels to maintain their mechanical integrity up to 180 °C. ILs and ion gels are suitable electrolyte candidates for thin-film devices operating at high temperatures because they outperform other electrolytes that use aqueous and organic solvents, owing to their superior thermal stability and nonvolatility. In addition to thermal stability, the PA gels exhibited high ionic conductivity (∼1 mS/cm) and specific capacitance (∼10 μF/cm²) at room temperature; these values increased significantly with increasing temperature, while the gel retained its solid-state mechanical integrity. These thermostable ion gels were successfully used as an electrolyte gate dielectric in organic thin-film transistors that operate at high temperatures (ca. 150 °C) and low voltages (<1 V). The transistors gated with the dielectrics had a high on/off current ratio of (3.04 ± 0.24) × 10⁵ and a hole mobility of 2.83 ± 0.20 cm²/V·s. By contrast, conventional physical ion gels based on semicrystalline polymers of poly(vinylidene fluoride-co-hexafluoropropylene) and polyvinylidene fluoride lost their mechanical integrity and dewetted from a semiconductor channel at lower temperatures. Therefore, these results demonstrate an effective method of generating thermally stable, mechanically robust, and highly conductive solid polymer electrolytes for electronic and electrochemical devices operating in a wide temperature range.

Responsive Ionogel Surface with Renewable Antibiofouling Properties

The synthesis of ionogels with a responsive, self-replenishing surface for combating biofouling is described. Ionogels are prepared by infiltrating poly(vinylidene fluoride-co-hexafluoropropylene) with binary mixtures of ionic liquids (IL): 1-octadecyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([C₁₈ C₁ im][NTf₂ ], melting point T_m = 55 °C) and 1-hexyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([C₆ C₁ im][NTf₂ ], T_m = -9 °C). The IL mixtures release spontaneously from the gel matrix and eventually crystallize on the surface. This leads to self-replenishment of the surface of ionogels even after mechanical damage. The incorporation of [C₆ C₁ im][NTf₂ ] provides the antimicrobial efficacy of ionogels while the crystals of [C₁₈ C₁ im][NTf₂ ] serve as a skeleton maintaining [C₆ C₁ im][NTf₂ ] on the surface. By heating, the ionogel surface transforms from solid to liquid-infused state-the removal of biofilms/bacteria developed under a long time of colonization is facilitated. The antimicrobial efficacy is maintained even after several cycles of biofilm formation and detachment. This work provides an opportunity to apply ionogels as functional coatings with renewable antibiofouling properties.

Ultrasensitive Interfacial Capacitive Pressure Sensor Based on a Randomly Distributed Microstructured Iontronic Film for Wearable Applications

The rapid development of pressure sensors with distinct functionalities, notably, with increased sensitivity, fast response time, conformability, and a high degree of deformability, has increased the demand for wearable electronics. In particular, pressure sensors with an excellent sensitivity in the low-pressure range (<2 kPa) and a large working range simultaneously are strongly demanded for practical applications in wearable electronics. Here, we demonstrate an emerging class of solid polymer electrolyte obtained by incorporating a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide with poly(vinylidene fluoride- co-hexafluoropropylene) as a high-capacitance dielectric layer for interfacial capacitive pressure sensing applications. The solid polymer electrolyte exhibits a very high interfacial capacitance by virtue of mobile ions that serve as an electrical double layer in response to an electric field. The randomly distributed microstructures created on the solid electrolyte help the material to elastically deform under pressure. Moreover, the interfacial capacitance is improved by utilizing a highly conductive porous percolated network of silver nanowires reinforced with poly(dimethylsiloxane) as the electrodes. An ultrahigh-pressure sensitivity of 131.5 kPa^-1, a low dynamic response time of ∼43 ms, a low limit of detection of 1.12 Pa, and a high stability for over 7000 cycles are achieved. Finally, we demonstrate the application of the sensor for international Morse code detection, artery pulse detection, and eye blinking. Owing to the ultrahigh sensitivity, the as-fabricated sensor will have great potential for wearable devices in health status monitoring, motion detection, and electronic skin.

Mechanical and self-recovery properties of supramolecular ionic liquid elastomers based on host–guest interactions and correlation with ionic liquid content

Supramolecular materials have received considerable attention due to their higher fracture energy and self-recovery capability compared to conventional chemically cross-linked materials. Herein, we focus on the mechanical properties and self-recovery behaviours of supramolecular polymeric elastomers swollen with ionic liquid. We also gained insight into the correlation between ionic liquid content and mechanical properties. These supramolecular polymers with ionic liquid can be easily prepared from bulk copolymerization of the host–guest complex (peracetylated cyclodextrin and adamantane derivatives) and alkyl acrylates and subsequent immersion in ionic liquid such as 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The supramolecular polymeric elastomers showed a self-recovery ability, which the conventional chemically cross-linked elastomers with ionic liquid cannot achieve.

Supramolecular ionic liquid elastomers showed higher fracture energy than chemically cross-linked ionic liquid elastomers and also self-recovery ability.

Sub-2 V, Transfer-Stamped Organic/Inorganic Complementary Inverters Based on Electrolyte-Gated Transistors

Organic/inorganic hybrid complementary inverters operating at low voltages (1 V or less) were fabricated by transfer-stamping organic p-type poly(3-hexylthiophene) (P3HT) and inorganic n-type zinc oxide (ZnO) electrolyte-gated transistors (EGTs). A semicrystalline homopolymer-based gel electrolyte, or an ionogel, was also transfer-stamped on the semiconductors for use as a high-capacitance gate insulator. For the ionogel stamping, the thermoreversible crystallization of phase-separated homopolymer crystals, which act as network cross-links, was employed to improve the contact between the gel and the semiconductor channel. The homopolymer ionogel-gated P3HT transistor exhibited a high hole mobility of 2.81 cm²/(V s), and the ionogel-gated n-type ZnO transistors also showed a high electron mobility of 2.06 cm²/(V s). The transfer-stamped hybrid complementary inverter based on the P3HT and ZnO EGTs showed a low-voltage operation with appropriate inversion characteristics including a high voltage gain of ∼18. These results demonstrate that the transfer-stamping strategy provides a facile and reliable processing route for fabricating electrolyte-gated transistors and logic circuits.