High-Toughness and High-Strength Solvent-Free Linear Poly(ionic liquid) Elastomers

Synergistic Liquid Metal-Diamond-Reinforced Poly(ionic liquid) Composites for High Thermal Conductivity and Excellent Reliability

This study presents a thermally conductive composite material that combines poly(ionic liquid) (PIL) poly(1-octyl-3-vinylimidazole)bis(trifluoromethanesulfonyl)imide (P[OVIm]NTf2), liquid metal (LM), and diamond as dual fillers, totaling 85 vol % loading. The composite achieves a thermal conductivity of 14.2 W m-1 K-1, a tensile elongation of 74%, and an interfacial adhesion strength of 0.99 MPa on steel substrates. Structural optimization and interfacial engineering contribute to its exceptional mechanical flexibility and processability, confirmed by dynamic rheological analysis. In chip packaging tests, the composite enhances heat dissipation efficiency by reducing interfacial thermal resistance. Diamond incorporation prevents LM oxidation, maintaining 99% surface coverage and minimal performance degradation after aging tests (-55 to 125 °C, 300 cycles; 150 °C, 1000 h). Chromium-plated diamond further improves reliability under high humidity and temperature. This ternary system resolves the trade-off between high filler loading and flexibility in thermal interface materials. Interfacial reinforcement and synergistic stabilization mechanisms balance thermal conductivity with long-term reliability. These findings promote the use of poly(ionic liquid)s in thermal management, offering a durable solution for high-power electronics, especially in extreme conditions. The study establishes a framework for designing advanced TIMs with optimized performance and stability.

Stretchable, Adhesive, Self-healing, High-efficiency Microwave Absorption by a Gel-Like Single-Component Poly(ionic liquid)

Fabrication of gel-based microwave absorbers is an effective strategy for overcoming the shortcomings of conventional powder-like absorbers, such as complicated processes and undesirable properties. However, the present gel-based microwave absorbers generally consist of a polymer skeleton and a liquid dispersion medium and suffer from leakage of the dispersion medium. In this study, a novel gel-like poly(ionic liquid) (PIL) microwave absorber with excellent properties is prepared. A maximum reflection loss (RLmax) of -58.8 dB GHz and an effective absorption bandwidth (EAB) of 10.56 GHz are achieved, which is mainly ascribed to high ionic conduction loss derived from lower glass transition temperature (Tg). Furthermore, the prepared PILs consisted of cationic imidazole-containing alkoxy moieties as the polymer chain and bis(trifluoromethanesulfonyl) imide (TFSI-) as the counter ion in the absence of a dispersion medium. The PILs displayed stretchability and adhesive and self-healing abilities, thus providing a new candidate for developing high-efficiency microwave absorbers for practical applications.

Compression-Durable Soft Electronic Circuits Enabled by Embedding Self-Healing Biphasic Liquid-Solid Metal Into Microstructured Elastomeric Channels

Compression strongly degrades the electrical conductivity of the liquid-metal-based circuits because the liquid state is prone to be squashed. Here, a new compressible and stretchable biphasic liquid-solid self-healing circuit is proposed by filling GalnSn-BilnSn biphasic metal into micropillar-embedded channels. The underlying BilnSn solid alloy layer serves as a compression resistance layer, while the upper GalnSn liquid metal layer enables the real-time filling of the cracks in the solid layer under large deformations, resulting in autonomous self-healing and maintenance of conductivity under both stretching and compression. The embedded micropillars further improved the compression durability by providing additional mechanical support. The synergistic effect between the biphasic materials and embedded micropillar enables the designed stretchable conductor to show stable performance (R/R0<10) under pressure of 38.2 MPa (≈389.5 Kgf cm-2) and cyclic pressure of 15.8 MPa over 7000 cycles (R/R0<0.48%) without compromising the stretchability, whereas the liquid metal-based conductor can only endure pressure up to 2.5 MPa (25.49 Kgf cm-2). The stretchable antenna and hybrid circuits fabricated using the designed biphasic metal conductor showed enhanced compression durability. The structure-confined filling strategy enabled high-resolution and scalable manufacturing. Overall, robust stability under compression significantly expands the range of possible applications of liquid-metal-based conductors in soft electronics.

Highly ionic conductive, elastic, and biocompatible double-network composite gel for epidermal biopotential monitoring and wearable sensing

Soft ionic conductors are promising candidates for epidermal electrodes, flexible sensors, ionic skins, and other soft iontronic devices. However, their inadequate ionic conductivity and mechanical properties (such as toughness and adhesiveness) are still the main constraints for their wide applications in wearable bioelectronics. Herein, an all-biocompatible composite gel with a double-network (DN) strategy is proposed. Compared to the single network, introducing a double-helix structured ι-carrageenan facilitates the DN gel with greatly enhanced mechanical properties and higher ionic conductivity (16.0 mS cm-1). Moreover, the DN gels exhibit high transparency (>92 %), high stretchability (1660 %), and sufficient adhesion. Benefiting from the above unique features, the DN gels successfully serve as biopotential electrodes, which can dynamically monitor human electrophysiological signals with a higher signal-to-noise ratio and superior environmental stability than the commercial electrode. Additionally, they can be employed as resistive strain sensors for accurate human movement monitoring. Our multifunctional DN composite gels offer a feasible platform for on-skin bioelectronics and human-machine interactions.

Ion transport in helical-helical polypeptide polymerized ionic liquid block copolymers

Helical-helical polypeptide polymerized ionic liquid block copolymers (PPIL BCPs) are synthesized to investigate the role of helical structure on self-assembly and ionic conductivity. PPIL BCPs, consisting of a cationic polypeptide (PTPLG) with bis(trifluoromethane sulfonimide) (TFSI) counterion and varying lengths connected to a length-fixed neutral poly-(γ-benzyl-L-glutamate) (PBLG) block, exhibit stable helical conformations with minimal glass transition (Tg) variation. Here, we show that increasing PIL composition leads to a transition from poorly ordered to highly ordered lamellar (LAM) structures with the highest PIL content BCP forming a bilayer LAM structure with close-packed helices. This morphology yields a 1.5 order of magnitude higher Tg- and volume fraction-normalized ionic conductivity and a morphology factor f > 0.8 compared to less ordered BCPs with f < 0.05 and f = 2/3 for ideal lamellae. These results highlight the critical role of helical structure in optimizing ion transport, offering a design strategy for high-performance solid electrolytes.

Bifunctional Electrospun Nanocomposite Dressing: Integrating Antibacterial Efficacy and Controllable Antioxidant Properties for Expedited Wound Healing

Current wound dressings are insufficient in simultaneously addressing bacterial infections and oxidative stress, which severely affects wound healing outcomes. To solve this problem, we introduced poly(ionic liquid) (PIL) with strong antibacterial properties and cerium oxide nanoparticles (CeO2NPs) with excellent antioxidant capabilities into polyacrylonitrile (PAN) nanofiber membranes to prepare a novel composite dressing. The PIL-CeO2NPs-PAN nanofiber membrane provides sustained antibacterial activity through stably embedded PIL, while the uniformly distributed CeO2NPs achieve controlled release, avoiding safety issues caused by the rapid release of active substances. In vitro and in vivo experiments demonstrated that the membrane exhibits outstanding biocompatibility, significant antibacterial effects (inhibition rates of 88.3% against Escherichia coli and 93.2% against Staphylococcus aureus), and excellent antioxidant performance (64.7% reactive oxygen species scavenging rate). More importantly, PIL-CeO2NPs-PAN achieved a 94.1% wound healing rate within 14 days, significantly superior to traditional treatment methods. The results indicate that this composite membrane significantly improves wound healing by simultaneously resisting infection and oxidative stress, providing a safe and effective new option for clinical applications. Our work offers an innovative design strategy that combines antibacterial and antioxidant mechanisms for wound care.

Halometallate Ionic Liquid Dynamically Regulates Zwitterionic Hydrogels by Synergistic Multiple‐Bond Networks

Improving the compatibility between high concentration metallic ions and zwitterions to controllable construction of coordination bonds is critical and extremely challenging. Here, a facile and effective strategy to fabricate multifunctional hydrogels by randomly copolymerizing halometallate ionic liquids (ILs) and zwitterions through electron beam irradiation is reported. Introducing metal ions into ILs can balance charges and establish moderate and stable cross‐linked networks with zwitterions. The synergistic effect of coordination bonds and multiple interactions with varying strengths endows hydrogel with outstanding stretchability, compressive strength, rapid response, advanced self‐healing ability, and excellent frost resistance. The multifunctional sensor assembled from hydrogels can timely, accurately, and stably monitor human movement, write anti‐counterfeiting and remotely transmit Morse code signals. Multiple hydrogel sensors are also assembled into a flexible sensor array to track the tactile trajectory and detect spatial distribution of force. Moreover, the obtained hydrogel displays high temperature sensitivity with resistance temperature coefficient of −3.85% °C−1 at 25–40 °C, which can detect tiny temperature changes (0.1 °C). Interestingly, the processed hydrogel can effectively modulate the transmissivity through salt triggering to achieve patterning. Considering the structural designability of halometallate ILs, this work provides new insights for the development of multifunctional hydrogels.

Predicting Fatigue Damage in Hydrogels Through Force-Induced Luminescence Enhancement

Fatigue damage of polymers occurs under long-term load cycling, resulting in irreversible fracture failure, which is difficult to predict. The real-time monitoring of material fatigue damage is of great significance. Here, tough hydrogels are prepared with force-induced confined luminescence enhancement of carbonated polymer quantum dot (CPD) clusters to realize the visualization of fracture process and the monitoring of fatigue damage. The enhanced interactions induced by force between the clusters and the polymer in the confined space inhibit the non-radiative leaps and promote the radiative leaps to quantify the fatigue damage into optical signals. Rigid CPDs with abundant active sites on the surface can form dynamic reversible bonds with polymer and dissipate stress concentration, which significantly enhances the crack propagation strain (8000%) and fracture energy (26.4 kJ m-2) of hydrogels. CPD hydrogels have a wide range of applications in novel information encryption and luminescent robotics.

Optically transparent and mechanically tough glass with impact resistance and flame retardancy enabled by covalent/supramolecular interactions

Exploring glass materials beyond inorganic components represents a new direction in the development of artificial transparent materials. Inspired by the successes of polymeric and supramolecular glasses, we shifted our attention to the preparation of a transparent glass through the polymerization of low-molecular-weight monomers that are naturally tailored with noncovalent recognition motifs. In this work, an imidazolium unit bearing a vinyl group and a tetrafluoroborate counter anion was selected to construct an artificial glass. Experimental and theoretical investigations revealed that the cross-linking behavior of anions effectively transformed linear polymeric chains into three-dimensional networks. The polymeric-supramolecular glass exhibits a tough tensile strength (61.31 MPa), high Young's modulus (1.17 GPa), and good optical transparency (>90%), which are comparable to those of polymethyl methacrylate. Moreover, the obtained glass maintains excellent mechanical toughness and optical transparency over a wide temperature range (from -150 to 150 °C). The material shows a superior impact resistance (18.34 kJ m-2) and flame retardancy (V0 rating), which are barely achieved by supramolecular materials.

Ion-Specific Interactions Engender Dynamic and Tailorable Properties in Biomimetic Cationic Polyelectrolytes

Biomaterials such as spider silk and mussel byssi are fabricated by the dynamic manipulation of intra- and intermolecular biopolymer interactions. Organisms modulate solution parameters, such as pH and ion co-solute concentration, to effect these processes. These biofabrication schemes provide a conceptual framework to develop new dynamic and responsive abiotic soft material systems. Towards these ends, the chemical diversity of readily available ionic compounds offers a broad palette to manipulate the physicochemical properties of polyelectrolytes via ion-specific interactions. In this study, we show for the first time that the ion-specific interactions of biomimetic polyelectrolytes engenders a variety of phase separation behaviors, creating dynamic thermal- and ion-responsive soft matter that exhibits a spectrum of physical properties, spanning viscous fluids to viscoelastic and viscoplastic solids. These ion-dependent characteristics are further rendered general by the merger of lysine and phenylalanine into a single, amphiphilic vinyl monomer. The unprecedented breadth, precision, and dynamicity in the reported ion-dependent phase behaviors thus introduce a broad array of opportunities for the future development of responsive soft matter; properties that are poised to drive developments in critical areas such as chemical sensing, soft robotics, and additive manufacturing.

Poly(ionic liquid)s: A Promising Matrix for Thermal Interface Materials

The swift progression of high-density chiplet packaging, propelled by the artificial intelligence revolution, has precipitated a critical need for high-performance chip-scale thermal interface materials (TIMs). The elevated thermal resistance, limited interfacial adhesion, and mechanical flexibility intrinsic to silicone systems present a substantial challenge in meeting reliability standards amidst chip warpage. This particular matter underscores a significant performance bottleneck within existing high-end TIMs. In this study, we present poly(ionic liquid)s (PILs) as an innovative matrix for TIMs. Our findings highlight the unique properties of PILs, showcasing a low elastic modulus (60 kPa), exceptional flexibility and stretchability (>3800%), high adhesion to diverse substrates (up to 4.10 MPa), favorable filler compatibility, remarkable thermal stability, and prompt self-healing capabilities coupled with recyclability. The collective findings suggest that the PIL serves as an ideal matrix for heat transfer. As a proof of concept, PIL blended with liquid metal was straightforwardly combined to produce a TIM, exhibiting exceptional performance within practical encapsulated structures. The PIL-based TIM demonstrates substantial elongation at break (>350%), coupled with sustained high adhesion strength (up to 1.70 MPa), and exhibits favorable thermal conductivity in package testing. This study presents an innovative TIM matrix with the potential to enhance existing TIM systems, delivering significant performance benefits compared to silicones. Besides elucidating their multifaceted characteristics, this study forecasts an expanded range of applications for PILs, along with laying the groundwork for advancing next-generation TIMs.

A Solid-Liquid Bicontinuous Fiber with Strain-Insensitive Ionic Conduction

Stretchable ionic conductors are crucial for enabling advanced iontronic devices to operate under diverse deformation conditions. However, when employed as interconnects, existing ionic conductors struggle to maintain stable ionic conduction under strain, hindering high-fidelity signal transmission. Here, it is shown that strain-insensitive ionic conduction can be achieved by creating a solid-liquid bicontinuous microstructure. A bicontinuous fiber from polymerization-induced phase separation, which contains a solid elastomer phase interpenetrated by a liquid ion-conducting phase, is fabricated. The spontaneous partitioning of dissolved salts leads to the formation of a robust self-wrinkled interface, fostering the development of highly tortuous ionic channels. Upon stretch, these meandering ionic channels are straightened, effectively enhancing ionic conductivity to counteract the strain effect. Remarkably, the fiber retains highly stable ionic conduction till fracture, with only 7% resistance increase at 200% strain. This approach presents a promising avenue for designing durable ionic cables capable of signal transmission with minimal strain-induced distortion.