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Dynamics of exchange within vitrimer networks are influenced by mobility of the chemical species involved in the exchange reaction, then it can be affected by the crystalline phase when boronic ester bond is introduced into the thermoplastic elastomers with crystalline phase as physical cross-links. In this work, the dynamic dioxaborolane cross-links were introduced into commercial poly(ethylene-α-octene) (POE) with crystalline phases as physical cross-links to prepare POE vitrimers. The results of stress relaxation show that relaxation time (τ) follows an Arrhenius law with the temperature at the melting range for not only POE vitrimers and thermally treated POE vitrimers with dynamic cross-links, but also neat POE with purely physical cross-links. The liquid-to-solid transition temperature can raise to 35.3 °C for POE vitrimers from -42.9 °C of the thermally treated one, due to the constrained mobility by residual crystalline phases. The resulted POE vitrimers maintain a stress at break of higher than 27.5 MPa and an elongation at break of higher than 800% at room temperature. With the temperature increasing, the crystal melting induced weakening of the physical cross-linking in POE decreases the strength, but the storage modulus and the stress at 300% and 500% elongation of POE vitrimers are improved. The properties of POE vitrimers can almost keep unchanged after recycling or healing. All these results show that the introduction of reversible boronic ester bonds is a promising strategy to improve the performances and recyclability of physically cross-linked POE materials. [ABSTRACT FROM AUTHOR]

• A solvent-exchange induced hydrogen bond activation strategy for gel actuators is developed. • The gel shows abnormal swelling behavior due to glycerol releasing during water immersing. • The self-adaptive organohydrogel actuator exhibits excellent mechanical properties. • The twisted actuator shows a high actuation rate and humidity-induced actuation performance. Hydrogel actuators have aroused tremendous interests in various fields such as artificial muscles, biomedicine and wearable devices. However, hydrogel actuators face persistent challenges due to their intrinsic weak and hydrophilic networks, which result in brittle and weak mechanical properties after swelling. Here, we proposed a solvent-exchange hydrogen bond activation strategy to fabricate a highly strong and tough self-adaptive organohydrogel actuators (SOA). The glycerol releasing and water retention triggers abnormal swelling of SOA due to the cross-linking of tannic acid (TA) and polyvinyl alcohol (PVA) nanofibrillar network. After the hydrogen bond activation between PVA and TA, SOA shows a denser and porous nanofibrillar network with high tensile strength (5.4 ± 0.2 MPa), high fracture energy (134.9 ± 7.6 kJ/m2), and high toughness (18.5 ± 0.7 MJ/m3). Owing to its good processibility, an anisotropic multi-filament twisted fiber actuator that exhibits ultra-high modulus (83.5 ± 2.6 MPa) and humidity-sensitive actuation performance was developed. The proposed solvent-exchange strategy shows great potential for the rational design and fabrication of bionic strong and tough artificial muscles. [ABSTRACT FROM AUTHOR]

An isotactic polypropylene (iPP) nanocomposite with low percolation threshold, ultrahigh dielectric permittivity and toughness by controlling the dispersion of multi-walled carbon nanotubes (MWCNTs) through ethylene-α-octene block copolymer (OBC), is reported. A special ‘sosatie’ structure, i.e. finely dispersed long MWCNTs inserted in OBC phase uniformly distributed in the continuous iPP matrix, was constructed through simple melt compounding process. The percolation threshold of the prepared iPP/OBC/MWCNT nanocomposites was ca. 0.5 vol%, lower than that of iPP/MWCNT nanocomposites. The iPP/OBC/MWCNT nanocomposites exhibited an ultrahigh dielectric permittivity (ca. 9000) at 100 Hz and a very low dielectric loss (ca. 1.5). MWCNTs also improved the compatibility between iPP and OBC components, leading to a high impact strength of iPP/OBC/MWCNT nanocomposites (about 13 times higher than pure iPP when the content of MWCNT was 1.49 vol%). Thus, the approach reported in this work can provide a new and convenient route to prepare high-performance polymer nanocomposite dielectric materials with low percolation thresholds and balanced mechanical properties. [ABSTRACT FROM AUTHOR]

Most stretchable film strain sensors generally present nonlinear electrical responses to applied strain, leading to an inaccurate acquisition of sophisticated signals, difficult signal processing, and zero‐calibration, which hampers practical applications severely. Here, a Janus hetero‐structured microarray film sensor is developed by in‐situ growth of silver nanoparticles on the surface of micro‐patterned elastomer films fabricated via low‐temperature imprinting followed by scraping‐induced particle trapping. Heterogeneous property designs in both modulus and electrical conductivity via introducing polymer microarrays enable modulating the electron transport manner in the conductive layer of elastic Janus films upon stretching, allowing to tune signal linearity effectively. Therefore, such a hetero‐structured film sensor shows good signal linearity (fluctuation of gauge factor [GF] below ±0.02) and relatively high sensitivity (GF > 10) within 55% strain, a detection limit of 0.2% strain, and a response/recovery time of 16.3/46.9 ms, respectively. Correspondingly, it enables monitoring human respiration and body motion with higher resolution compared with the nonlinear one, meanwhile, it is capable of detecting tiny pressure to discriminate braille alphabets via touch identification. Overall, it unveils a simple strategy to fabricate film strain sensors for high‐resolution healthcare and body motion monitoring, as well as electronic skins toward tactile sensing and touch identification. [ABSTRACT FROM AUTHOR]

Effects of aspect ratio of multi-wall carbon nanotubes (MWCNTs) on the dispersion of MWCNTs in ethylene-α-octene block copolymer (OBC) and the properties of OBC/MWCNTs nanocomposites were studied, and two series of MWCNTs with different aspect ratios based on the same length and the same diameter were considered. Scanning electron microscope (SEM) and transmission electron microscope (TEM) results show that small and large agglomerates induced by intra- and inter-entanglement of MWCNTs are present for MWCNTs with high aspect ratio having smaller diameter and larger length, respectively. Rheological, electrical and tensile properties of OBC/MWCNTs nanocomposites are related to the aspect ratio and dispersion of MWCNTs. The formation of agglomerates, especially large agglomerates, influence the network perfection, weakening the contribution of MWCNTs to the rheology and electrical properties. The inter-entanglement shows less negative effect on the enhancement for the modulus and strength of OBC nanocomposites, and intra-entanglement of MWCNTs shows discounted enhancing properties. The aspect ratios of MWCNTs related to not only the length but also the diameter play the dominant role on the dispersion in polymers and the properties of polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Stretchable electrodes play a crucial role in wearable electronics for high-efficiency carrier transport in the information communication, yet it is challenging to achieve high electrical conductivity at large strain for stretchable and porous conductive composites. Here, a simple yet efficient strategy is proposed to fabricate highly conductive, porous and stretchable composites via seeding hydrophilic carbon nanotube (CNT) oil-in-water microemulsions in elastomer films prior to growing silver nanoparticles (AgNPs) in situ. It aims at forming a dual heterogeneous structure of CNT microspheres in the elastomeric films containing conductive networks of AgNPs, which allow to guarantee the overall good electrical conductivity. Unlike the rapid propagation of cut-through microcracks in conventional conductive network of AgNPs under strain, the mechanical and electrical dual hetero-structured CNT microspheres in the conductive networks can sustain high electrical conductivity at large strains by blocking and cutting off microcrack propagation. Therefore, the porous composite electrodes show electrical conductivity above 103 S/cm at 200% strain thanks to the efficient dissipation of strain energy by dual hetero-structured CNT microspheres, which is controlled by CNT concentration in the oil-in-water microemulsions. Besides, the as-fabricated porous composites sustain high yet stable electrical conductivity at various kinds of mechanical deformations, such as tension, bending, twisting and a combination of them, allowing for the promising application in stretchable and wearable electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

Macrophages are highly heterogeneous and exhibit a diversity of functions and phenotypes. They can be divided into pro‐inflammatory macrophages (M1) and anti‐inflammatory macrophages (M2). Diabetic wounds are characterized by a prolonged inflammatory phase and difficulty in healing due to the accumulation of pro‐inflammatory (M1) macrophages in the wound. Therefore, hydrogel dressings with macrophage heterogeneity regulation function hold great promise in promoting diabetic wound healing in clinical applications. However, the precise conversion of pro‐inflammatory M1 to anti‐inflammatory M2 macrophages by simple and biosafe approaches is still a great challenge. Here, an all‐natural hydrogel with the ability to regulate macrophage heterogeneity is developed to promote angiogenesis and diabetic wound healing. The protocatechuic aldehyde hybridized collagen‐based all‐natural hydrogel exhibits good bioadhesive and antibacterial properties as well as reactive oxygen species scavenging ability. More importantly, the hydrogel is able to convert M1 macrophages into M2 macrophages without the need for any additional ingredients or external intervention. This simple and safe immunomodulatory approach shows great application potential for shortening the inflammatory phase of diabetic wound repair and accelerating wound healing. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI), as a common oxidative stress‐related renal disease, causes high mortality in clinics annually, and many other clinical diseases, including the pandemic COVID‐19, have a high potential to cause AKI, yet only rehydration, renal dialysis, and other supportive therapies are available for AKI in the clinics. Nanotechnology‐mediated antioxidant therapy represents a promising therapeutic strategy for AKI treatment. However, current enzyme‐mimicking nanoantioxidants show poor biocompatibility and biodegradability, as well as non‐specific ROS level regulation, further potentially causing deleterious adverse effects. Herein, the authors report a novel non‐enzymatic antioxidant strategy based on ultrathin Ti3C2‐PVP nanosheets (TPNS) with excellent biocompatibility and great chemical reactivity toward multiple ROS for AKI treatment. These TPNS nanosheets exhibit enzyme/ROS‐triggered biodegradability and broad‐spectrum ROS scavenging ability through the readily occurring redox reaction between Ti3C2 and various ROS, as verified by theoretical calculations. Furthermore, both in vivo and in vitro experiments demonstrate that TPNS can serve as efficient antioxidant platforms to scavenge the overexpressed ROS and subsequently suppress oxidative stress‐induced inflammatory response through inhibition of NF‐κB signal pathway for AKI treatment. This study highlights a new type of therapeutic agent, that is, the redox‐mediated non‐enzymatic antioxidant MXene nanoplatforms in treatment of AKI and other ROS‐associated diseases. [ABSTRACT FROM AUTHOR]

Big volume changes, the shuttle effect, and poor conductivity are well‐known, critical issues of sulfur electrodes that prevent practical application of lithium‐sulfur batteries. The design of active materials with a conductive shell provides an effective solution. Traditional strategies have long been limited for practical applications; however, by low productivity and time/energy consuming template‐based methods. Here, a facile template‐free self‐caging nanotechnology for the scalable fabrication of graphene@sulfur nanocages with atomic‐scale shells is reported. To do that, a new sulfur‐graphene nanochemistry based on a reductive sulfur solution and oxidative sulfonated‐graphene dispersion is developed for the first time. With only the help of mechanical mixing, sulfur particles are successfully synthesized in situ and encapsulated into reaction‐induced self‐assembled sulfonated‐graphene nanocages. These unique nanocages not only provide accommodation of the big volume changes in the active materials, but also exhibit robust polysulfide trapping capability due to the synergistic effects from physical blocking and strong chemical absorption. As a result, the resultant sulfur cathodes deliver superior electrochemical performance and have shown an extremely slow capacity decay of 0.019% per cycle at 0.5 C for over 2000 cycles. This study introduces a new self‐caging nanochemistry for scalable synthesis of functional nanocages with significant applications beyond lithium‐sulfur batteries. [ABSTRACT FROM AUTHOR]

• The solid network structure of ionogel is regulated by ionic liquids. • Ionogel exhibits modulus similar to skin and excellent mechanical properties. • Ionogel exhibits high ionic conductivity and good thermoelectric performance. • Supercapacitors prepared from ionogel can perform intermittent thermal conversion. Thermoelectric (TE) materials can directly convert heat into electricity, which is of great significance to sustainable development. Thermoelectric ionogels have received extensive attention due to high thermopower and excellent flexibility. However, their low ionic conductivity and poor mechanical properties severely limit their potential applications. Here, engineering the solid network structure of polyvinyl alcohol (PVA) hydrogel by ionic liquids (IL) significantly improves the ionic conductivity as well as the overall thermoelectric properties and mechanical properties. The introduction of 1-ethyl-3-methylimidazolium dicyanamide (EMIM:DCA) into PVA solution before the formation of PVA/IL ionogels reduces the mobility of polymer chains, resulting in significantly reduced crystal size. Thus, the microstructure of PVA/IL ionogels promotes the ion transport ability. The ionic conductivity of PVA/IL ionogels increases from 0.77 to 2.78 S m−1, resulting in a power factor 70 times higher than that of PVA hydrogel. In addition, the abundant microcrystalline regions in PVA/IL ionogels with nanoscale network structure can dissipate a large amount of energy and endow the PVA/IL ionogels with excellent mechanical properties, which can greatly broaden the application potential of ionogels. [ABSTRACT FROM AUTHOR]

A flexible strain sensor is developed via one-step in-situ construction of stiff PVDF nanospheres on the surface of TPU fibers via polymeric phase and morphology control technology. It enables tunable linear sensing to strain thanks to the restricting of quick crack propagation. [Display omitted] • Flexible fiber mat strain sensors of heterogeneous structures are developed. • The heterogeneous structure is consisted of stiff PVDF nanospheres on TPU fibers. • The structure can restrict quick micro-crack propagation throughout fiber surface. • The sensor with high-density nanospheres shows very good linearity. Wearable strain sensors with high sensitivity and linear resistance signal response to strain are urgently demanded for human–machine interface, which can be tuned by introducing uneven surface mechanics distribution onto fiber surfaces via structural heterogeneity for fibrous elastomer fiber mat sensors. Yet it is still of great challenge to build micro- or nano-scale heterogeneous structures on fiber surfaces in a facile and scalable way without using templates. Herein, we report a plastic nanosphere-decorated elastomer fiber mat strain sensor with a zoned surface strain energy release characteristic, designed based on analysis of material match and structural mechanics. Surface mechanics analysis confirms that the as-designed sensor shows a controllable strain energy release area, significantly improving sensing stability thanks to effective restriction of micro-crack propagation in conductive pathways. In particular, fibrous mat sensor with high-density nanospheres shows very low fluctuation in strain sensitivity variation (±0.05 for strain ≤ 30 %), i.e., good linearity in the resistance response to strain, while that for the control sensor is ± 10.0 for strain ≤ 16 %. Such a fiber mat strain sensor can not only be applied for real-time sensing of object deformations for human–machine interface and intelligent control, but also in hydrophobic porous elastomeric packaging materials and triboelectric devices. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) based stretchable conductors have broad application due to their excellent conductivity and deformability. However, the poor interfacial interaction between LM and majority of elastic substrates because of the high surface tension of LM, limits the spread of LM on the substrate and the reconciliatory deformation of LM with underlying substrate. Herein, through the specific affinity between the immediately formed oxide layer on surface of eutectic gallium-indium (EGaIn) and carboxyl groups, an in-situ interfacial engineering for LM conductive coating on hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) (PEO/PAA) elastomers is presented. Particularly, EGaIn patterned on PEO/PAA elastomers can autonomously adapt to the mechanical deformation of substrates to form a stable interface conductive layer, and the slope of deformation ratio between EGaIn layer and PEO/PAA elastomers keeps nearly 1 even at strain of 800%. The design of interfacial interaction also ensures the simultaneous achievement of excellent stretchability and stable conductivity of LM based stretchable electronics, that is, the resistance of the EGaIn conductor will not change significantly and remain below 1 Ω even at a strain of 800%. This work provides guideline for the design of stretchable LM-based conductor. [Display omitted] • An in-situ interfacial engineering for LM on hydrogen-bonded PEO/PAA elastomers is presented. • Strong interaction occurs between oxide layer on surface of EGaIn and carboxyl groups. • The slope of deformation ratio between LM layer and PEO/PAA elastomers keeps nearly 1 even at strain of 800%. • The resistance of the LM-based conductor can remain below 1 Ω even at a strain of 800%. [ABSTRACT FROM AUTHOR]