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Potassium (K) is regarded as an alternative to lithium (Li) for use in contemporary energy storage devices owing to its high abundance and low electrochemical potential. However, because K ions are larger than Li ions, they exhibit different solvation properties that can ultimately affect device performance. Herein, a multidentate ether-based electrolyte is demonstrated to effectively solvate K ions and the solvation structures can be further modulated with cosolvents. The use of the multidentate ether-based electrolyte also suppresses the formation of K dendrites and significantly enhances the cycling stability of K//K symmetric cells (e.g., over 2000 h at 0.25 mA cm-2). © 2022 American Chemical Society. All rights reserved.

Fluorescence and RTP dual emission polymers exhibit reversible temperature responsiveness, tunable mechanical properties, remarkable thermostability and thermo-adaptive self-healing ability based on a dynamic covalently crosslinked 3D network.

A polymer with tunable multicolor was prepared via copolymerizing a phosphor with concentration dependent luminescence and acrylamide based on chemical crosslinking and hydrogen bonding interactions for humidity detection and information encryption.

Summary Mixed-halide perovskite provides band-gap tunability, which is essential for tandem solar cell application. However, ion migration inducing phase segregation seriously affects the device’s long-term operational stability. The issue thus represents an important challenge for the whole perovskite community and urgently needs effective solutions. We showcase here for the first time that a strong chemical interaction, a halogen-halogen bond, is introduced at the phase interface to suppress the ion migration by increasing the corresponding activation energy. Various characterizations have proved that halogen-halogen bonds form between 2D and 3D phases, which do suppress the halide segregation. As expected, the encapsulated device retains 90% of initial power conversion efficiency (PCE) after maximum power point (MPP) tracking for ∼500 h under continuous simulated 1-sun illumination (AM 1.5) in ambient conditions, representing one of the most stable, wide-band-gap, mixed-halide perovskite photovoltaics reported so far.

Polydopamine (PDA), with similar chemical and physical properties to eumelanin, is a typical artificial melanin material. With various functional groups, good biocompatibility, and photothermal conversion ability, PDA attracts great interest and is extensively studied. Endowing PDA with a porous structure would increase its specific surface area, therefore would significantly improve its performance in different application fields. However, creating abundant pores within the PDA matrix is a great challenge. Herein, a self-assembly/etching method is proposed to prepare hierarchically porous mesostructured PDA nanospheres. The oxidative polymerization of dopamine and hydrolysis of tetraethyl orthosilicate were coupled to co-assemble with a polyelectrolyte-surfactant complex template to form a mesostructured PDA/silicate nanocomposite. After removing templates and etching of silica, hierarchically porous PDA nanospheres were obtained with specific surface area and pore volume as high as 302 m

Conductive hydrogels have drawn tremendous attention in flexible devices, soft robotics, and artificial intelligence. The integration of synergistic characteristics such as reliable resilience, high strain sensitivity, and excellent mechanical properties is still a great challenge in strain sensors. Inspired by the heterogeneous network structure of biological soft tissues, herein, a novel ionic conductive hydrogel was fabricated by the interconnection between a “soft” hydrogen bond cross-linked polymeric network and “rigid” domains cross-linked by double hydrogen bonding, hydrophobic interaction, and π–π stacking. The completely physically cross-linked hydrogel exhibited excellent stretchable property (680%) and great resilience (92.53%). Besides, owing to numerous free moving ions (Li+, Na+, and Cl−) in the system, the hydrogel possessed high sensitivity (GF = 3.12) and fast strain responsiveness (≤100 ms) in a broad temperature range (−20–25 °C). Moreover, the hydrogel displayed tunable electromechanical behavior with durable stability and anti-fatigue variations in resistance upon mechanical deformation such as the detection of various daily human activities, including the variations of the fingers, elbow and larynx, and, jogging. Therefore, this “soft and rigid” structure provides a feasible solution for fabricating a high-performance ionic conductive hydrogel, which has potential as a multi-functional sensor in wearable devices, artificial intelligence, and electric skins.

Intelligent hydrogels that simultaneously exhibit excellent toughness, self-healing ability and photoelectronic responsiveness are in high demand but are greatly challenging to prepare. Inspired by the hierarchical structure of fluorescent proteins in jellyfish and biomembranes in nature, herein, a facile and universal all-in-one strategy is demonstrated to construct fluorescent, electrically responsive and ultratough self-healing hydrogels via aqueous self-assembly of polyelectrolyte-surfactant micelles with hierarchical structures and functionality. The self-assembled 2-ureido-4-[1H]-pyrimidone (UPy) hydrophobic core containing reversible physical crosslinks embedded in micelles leads to a durable network structure with excellent toughness and self-healing ability. Moreover, dramatically enhanced fluorescence emission is obtained due to the formation of nanoclusters with electron-rich moieties that show restricted intramolecular motion induced by hydrogen bonding networks from UPy dimer aggregation. The micelle-incorporated sulfonic acid groups mimic the function of biological membrane proteins that deftly control the micelle size, leading to electro-responsiveness, enhanced toughness and fluorescence emission.

Conductive materials with predominant mechanical properties and high sensitivity have promising applications in various fields such as fabrication of electric skins, wearable sensors, and soft robotics. High-performance and flexible strain sensors based on conductive hydrogels have attracted significant attention because of their potential applications in voice recognition and human–machine interfaces. Inspired by the mechanism of neural tissue signal transmission, herein, a high-strength and relatively high-sensitivity ionic conductive hydrogel was developed by utilizing the completely physically crosslinked polyvinyl alcohol (PVA) and a simple inorganic salt solution soaking strategy. The ionic conductive hydrogels exhibited intriguing remoldability and excellent mechanical properties such as superb tensile strength (8.03 MPa), high toughness (28.7 MJ m−3), and high elastic modulus (1 MPa) because of their high-density hydrogen bonding and chain entanglement networks. By integrating the PVA–NaCl gel into a flexible strain sensor, the sensor displayed high conductivity (7.14 S m−1) at room temperature and subzero temperature, high accuracy (GF = 0.989), and sensitive strain responsiveness in a wide strain detection window of 0.2–400%. These results imply good performance for monitoring and distinguishing various human daily activities and slight physiological signals. Furthermore, the as-made PVA sol could convert to gel state just by being injected on a flexible substrate under an ice-bath and the conductive hydrogels displayed excellent biocompatibility and improved cell proliferation. Therefore, the as-formulated hydrogel sensor can have promising applications in wearable devices, such as sports monitoring, healthcare monitoring or voice recognition.

Formic acid (FA) as a safe and promising hydrogen carrier has attracted widespread attention. The use of solid catalysts in the controllable and efficient dehydrogenation of FA is still a challenge. Here, a series of Au nanoclusters supported on rare earth metal doped ZrO2 catalysts (Au/ReZrO2 (Re = Nd, Ce and Sm)) was prepared. Doping rare earth metals in zirconia stabilizes the mixed-phase zirconia into the tetragonal phase. Meanwhile, the rare earth metal dopants can promote the formation of oxygen vacancies in zirconia, which promotes charge transfer from the support to Au and enhances the metal–support interaction on all the three catalysts. As a result, Au/ReZrO2 (Re = Nd3+, Ce3+ and Sm3+) catalysts exhibited better catalytic performance in the liberation of CO-free H2 from FA, outperforming Au supported on primary ZrO2. Structural and electronic characterization by XPS and H2-TPR further confirmed the contribution of doping rare earth metal cations in Au/ReZrO2, which can enhance the metal–support interaction and accelerate the decomposition of HCOOH into H2, thus resulting in the improvement in catalytic activity for hydrogen production from FA.

Nature embraces an intriguing strategy to create high-performance biomaterials, such as spider silk which presents an unparalleled combination of stiffness, tensile strength, and toughness via hierarchical structures. However, to fabricate synthetic polymers with such excellent properties remains a challenging task. Inspired by the integration of multiblock backbone and densely H-bonding assemblies in spider silk as well as the delicate iron-catecholate complexes in mussel byssus, we proposed a novel molecular design with multifunctional block modules to obtain polymer materials that exhibit excellent mechanical property, self-healing ability, and reprocessability. It was achieved by introducing reversible iron-catechol (DOPA-Fe

Nonprecious metal-based oxygen reduction reaction (ORR) electrocatalysts with high efficiency in both alkaline and acidic media are being intensively studied for the purpose of replacing expensive Pt-based catalysts; however, it is still a challenge to achieve superior ORR performances, especially in acidic media. Herein, by pyrolysis of mixed precursors of diammonium phosphate, melamine and hemin, we prepared a nanocomposite catalyst (denoted as FeP@PGL) composed of nitrogen-doped carbon nanosheets with embedded FeP nanoparticles (NPs), which were encapsulated by in-situ formed phosphorus-doped graphene layers. It is found that phosphorous was preferentially doped in the coating layers on FeP NPs, instead of in the carbon nanosheets. The FeP@PGL catalyst exhibited excellent ORR performance, with the onset and half-wave potential up to 1.01 and 0.90 V vs. the reversible hydrogen electrode (RHE) in alkaline media, and 0.95 and 0.81 V vs. RHE in acidic media, respectively. By thorough microscopy and spectroscopy characterizations, the interfacial charge transfer between the encapsulated FeP NPs and P-doped graphene layers was identified, and the local work function of the catalyst surface was also reduced by the interfacial interaction. The interfacial synergy between the encapsulated FeP and phosphorus-doped graphene layers was essential to enhance the ORR performance. This study not only demonstrates the promising ORR properties of the encapsulated-FeP-based nanocomposite catalyst, but also provides direct evidence of the interfacial charge transfer effect and its role in ORR process.

Thermoresponsive hydrogel-based actuators are highly important for fundamental research and industrial applications, while the preparation of temperature-driven bilayer hydrogel actuators with rapid response to bend and recover properties remains a challenge. To date, most temperature-driven bilayer hydrogel actuators are based on polymers only with a lower critical solution temperature (LCST) or with an upper critical solution temperature (UCST), which need more time to bend and recover just in a small range of bending angle. Herein, we propose a new strategy to design and synthesize a fully temperature-driven bilayer hydrogel actuator, which consists of a poly(N-acryloyl glycinamide) (NAGA) layer with a UCST-type volume phase change and a poly(N-isopropyl acrylamide) (NIPAM)-Laponite nanocomposite layer with an LCST-type volume phase change. Due to the complementary UCST and LCST behavior of the two selected polymers, both layers have opposite thermoresponsive swelling and shrinkage properties at low and high temperatures; this imbues the hydrogel actuator with rapid thermoresponsive bending and recovery ability, as well as a large bending angle. In addition, the incorporation of Laponite nanosheets in PNIPAM layer not only improves the mechanical property of actuators but also provides the excellent bonding ability of the two-layer interface, which prevents delamination caused by excessive local stress on the interface during the bending process. Thanks to high-performance behavior, the actuator can act as an effective and sensitive actuator, such as a gripper to capture, transport, and release an object, or as an electrical circuit switch to turn on and off a light-emitting diode (LED). Overall, such hydrogel actuator may provide new insights for the design and fabrication of artificial intelligence materials.

Tackling fogging and microbial infection problems related to the endoscope lens remain challenges due to visual disturbances and bacterial threats to human health. Herein, highly transparent antifogging and antibacterial coatings were developed in a facile way by thermal curing of zwitterionic copolymers poly(n-butyl methacrylate-co-2-aminoethyl methacrylate-co-sulfobetaine methacrylate)s with 1,3,5-triformylbenzene. Characterizations of surface chemical composition and wettability suggested that the copolymer coatings exhibited amphiphilicity with a hydrophobic surface and internal hydrophilicity. The prepared amphiphilic coating exhibited excellent antifogging properties both in vivo and in vitro. The introduction of hydrophobic n-butyl methacrylate and cationic aminoethylmethacrylate could improve the stability and antibacterial capability of the coating. The growth inhibition rates of the coatings against Staphylococcus aureus and Escherichia coli were up to 99% and the copolymer coatings with the zwitterionic groups had low hemolytic rates less than 3%. The amphiphilic copolymer coatings combined antifogging and antibacterial properties may have a promising potential for applications in biomedical devices.

The hierarchically porous silica (NKM-5) and aluminosilicate (Al-NKM-5) supported platinum nanoparticles catalysts were prepared and investigated for the catalytic combustion of toluene and ethanol...

Dynamic bonds have been widely incorporated into polymeric materials for achieving self-healing, recycling, and stimuli-responsive properties. As a result, these polymeric chains often exhibit dive...

The study on the design and preparation of oxygen reduction reaction (ORR) electrocatalysts with high efficiency is currently attracting great concern. Among different types of catalysts, heteroatom-doped carbon-based catalysts have exhibited promising potential, and the exploration of optimized matching of the doping elements is crucial to the design and fabrication of this category of catalysts. Herein, by annealing commercially available and cost-effective precursors, Fe-N-S codoped graphene-like carbon nanosheet catalysts were prepared. The atomically dispersed Fe atoms coordinated with the N atoms to form FeN4 sites as proved by X-ray absorption spectroscopy. By facile modulation of the relative amount of the precursors, the contents of thiophene-S (Th-S) and Fe-N4 sites could be tuned and a series of catalysts with different Th-S/Fe ratios were prepared. The doped sulfur exhibited an enhancement effect on ORR performance, and strikingly, the enhancement efficiency could be optimized by fine modulation of the Th-S/Fe ratio in the catalysts. Furthermore, it was found that when the Th-S/Fe ratio reached an optimal value of 1.8, the ORR performance was significantly boosted, especially in acidic media. The experimental data were supported by density functional theory calculation results, which indicated that the ORR overpotential of the S2(FeN4) configuration model (corresponding to the Th-S/Fe ratio of 2) was lower than that of S3(FeN4) and S1(FeN4). The optimized catalyst (denoted as FeN/SNC-900-3) displayed highly efficient ORR activity in both alkaline and acidic media. In alkaline media, the half-wave potential was 49 mV more positive than that of the commercial Pt/C catalyst, and in acidic media, the half-wave potential was close to that of Pt/C. Moreover, the stability of FeN/SNC-900-3 was outstanding, and the relative current density showed only a slight decay in both alkaline and acidic media after 40,000 s. A primary Zn-air battery with FeN/SNC-900-3 as the cathode catalyst exhibited a high peak power density of up to 153 mW cm-2 and superior cycling stability over 200 cycles.

Hierarchically porous materials have attracted great attention because of their potential applications in the fields of adsorption, catalysis, and biomedical systems. The art of manipulating different templates that are used for pore construction is the key to fabricating desired hierarchically porous structures. In this feature article, the polyelectrolyte-surfactant mesomorphous complex templating (PSMCT) approach, which was first developed by our group, is elaborated on. During the organic-inorganic self-assembly, the mesomorphous complex of the polyelectrolyte and oppositely charged surfactants would undergo in situ phase separation, which is the key to fabricating hierarchically porous materials. The recent progress in the utilization of the PSMCT method for the synthesis of hierarchically porous materials with tunable morphologies, mesophases, pore structures, and compositions is reviewed. Meanwhile, the functions of the hierarchically porous materials synthesized by the PSMCT method and their applications in adsorption, catalysis, drug delivery, and nanocasting are also briefly summarized.

Hydrogels with excellent conductivity and flexibility have a wide range of applications in the biomedical field, such as in wearable devices, soft electronic skins, and biosensors. Inspired by marine mussels, a biocompatible hydrogel with controllable adhesiveness and a wearable strain-sensor were successfully prepared by polymerization of N-isopropylacrylamide (NIPAM) and a dopamine-modified polypeptide (PDAEA). The PNIPAM-clay-PDAEA hydrogel displayed repeatable and controllable adhesiveness due to the presence of free catechol groups in the PDAEA chains and the intrinsic thermo-sensitivity of the PNIPAM-based hydrogel. These materials also exhibited outstanding strain and pressure sensitive conductivity, which could be ascribed to a sufficient number of free moving ions in the hydrogel system. Test results showed that these conductive hydrogels possessed excellent biocompatibility, stable drug release behavior, and improved cell proliferation. Therefore, the as-prepared nanocomposite hydrogel has great potential applications as a wearable soft electronic skin and in tissue engineering.

Physically crosslinked hydrogels with a reversible nature have attracted much attention in recent decades due to their fascinating self-recovery and self-healing properties, but the low mechanical strength hinders their development for many stress-bearing applications. In this study, inspired by the multiple supramolecular interactions in nature including hydrogen bonding and ionic bonds, we proposed a simple strategy to fabricate high-performance dual physically crosslinked D-hydrogels, which is triggered by the self-complementary quadruple hydrogen bonding interactions between 2-ureido-4[1H]-pyrimidinone (UPy) dimers and Fe3+ ionic coordination bonds as the dynamic sacrificial crosslinkers, thus obviously enhancing the mechanical strength and toughness. Due to the synergistic effect of the two types of physical crosslinking interactions, the D-hydrogels exhibit outstanding mechanical properties, such as a tensile strength of 7.9 MPa, an elastic modulus of 6.9 MPa, and an elongation at break of 541%, with an optimized structure. Furthermore, these reversible dual physical crosslinks enable the D-hydrogels to efficiently dissipate energy with a high toughness (up to 29 MJ m−3) while imparting good self-recovery properties, a pH-triggered healing capability and pH-responsive shape memory to the network. This dual physically crosslinked hydrogel with excellent mechanical performance as well as good recovery and self-healing properties will hopefully be exploited as a promising candidate for various biomedical applications.

A nano-confined pyrolysis approach was developed for constructing highly nitrogen-doped hierarchically porous metal/N/C nanospheres (typically Fe/N/C-HP). Hierarchically porous silica nanospheres (NKM-5) were used as a hard template, and an amorphous Fe/Zn-(MeIm)2 complex was employed as a carbon and nitrogen source. During the pyrolysis process, first, the molten Fe/Zn-(MeIm)2 complex diffused into hierarchically porous tunnels of NKM-5. Secondly, the interface confinement effect of nanopores in NKM-5 could effectively immobilize nitrogen to coordinate with iron atom, prevent the aggregation of Fe-based species and form single-atom Fe sites. After the silica template was removed, the catalyst exhibited a hierarchically porous structure and uniform spherical morphology. This hierarchically porous structure of Fe/N/C-HP can enhance mass transport/electron transfer and greatly improve the accessibility of Fe/N/C sites. As a result, the Fe/N/C-HP catalyst exhibits excellent oxygen reduction performance with a half-wave potential (E1/2) of 0.90 V in alkaline media and 0.78 V in acidic media. A primary Zn–air battery with Fe/N/C-HP as the cathode catalyst exhibits a large peak power density of 181 mW cm−2 and discharge stability. This nano-confined pyrolysis of amorphous M/Zn-(MeIm)2 complex is a general method to construct a hierarchically porous M/N/C (M = Fe, Co, Cu, Mn and Ni) electrocatalyst with well-defined morphology.

Understanding the structural evolution process after the yielding of networks in polymer nanocomposites can provide significant insights into the design and fabrication of high-performance nanocomposites. In this work, using hydroxyl-terminated 1,4-polybutadiene (HTPB)/organo-clay nanocomposite gel as a model, we explored the yielding and recovery process of a polymer network. Linear rheology results revealed the formation of a nanocomposite gel with a house-of-cards structure due to the fully exfoliated 6 to 8 wt% organo-clays. Within this range, nonlinear rheologic experiments were introduced to yield the gel network, and the corresponding recovery processes were monitored. It was found that the main driving force of network reconstruction was the polymer-clay interaction, and the rotation of clay sheets played an important role in arousing stress overshoots. By proton double-quantum (

As an important heterogeneous catalyst, Titanium Silicalite-1 (TS-1) zeolite has been widely applied in various catalytic processes. Here, hierarchical TS-1 single-crystals were successfully synthesized by a steam-assisted crystallization strategy using hierarchically porous titanium-containing silica (Ti-NKM-5) as a precursor. Due to the presence of large mesopores (10-40 nm)， the microporous structure-directing agents penetrated the interstitial structure of silica particles, inducing the dissolution and crystallization process. During crystallization, the generated nanocrystals grew together to form a hierarchical structure. Titanium was fully incorporated into the zeolite framework, and no extra-framework anatase was formed. Compared with the traditional microporous TS-1 zeolite, the synthesized hierarchical TS-1 single-crystal exhibited superior catalytic performance in oxidative desulfurization (ODS) of dibenzothiophene (DBT) and 4, 6-dimethyl dibenzothiophene (4, 6-DMDBT) owing to the hierarchically porous and anatase-free structure. The recycling test revealed the durability of the obtained hierarchical TS-1 catalyst under moderate reaction conditions.

Developing cost-effective and stable non-noble electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is now the critical issue for large-scale application of zinc-air batteries. Here, we presented a simple method to synthesize highly dispersed cobalt manganate spinel nanodots in-situ embedded in amine-functionalized carbon black. Silane coupling agent 3-aminopropyltriethoxysilane (APTES) played dual roles in the preparation: (1) to achieve amine-functionalization of carbon support; (2) as weak alkali to precipitate metal hydroxides which were then converted to spinel nanodots after mild calcination. The hydrophilicity of the carbon substrate was enhanced by amine modification from APTES to disperse metal oxide evenly, and the electrochemical activity was promoted through the strong interface interaction between embedded spinel nanodots and carbon substrate during the calcination process. As expected, the CoMn2O4/C-NH2-300 catalyst exhibited satisfactory bifunctional catalytic performance for both ORR and OER with an ΔE (E1/2-Ej10) = 0.75 V, which was lower than most state-of-the-art catalysts. In addition, CoMn2O4/C-NH2-300 as a cathode also exhibited remarkable zinc-air battery performance in alkaline solution. This strategy of APTES as a bifunctional coupling agent provided a novel way to design and explore highly active, durable, and cost-effective catalysts for renewable energy conversion and storage.

Direct polarization using a single pulse is the simplest excitation scheme in nuclear magnetic resonance (NMR) experiments, capable of quantifying various compositions in many materials applications. However, this single-pulse excitation generally gives rise to NMR spectra with a severely distorted baseline due to the background signals arising from probe components and/or due to the radio-frequency (RF) acoustic ringing, especially in low-γ nuclei and wide-line NMR. In this work, a triple-pulse excitation scheme is proposed to simultaneously suppress the background signals and eliminate the RF acoustic ringing. The acoustic ringing is cancelled through subtraction in any two consecutive scans by alternating the receiver phase while keeping the phase of the pulse right before acquisition the same. While the triple-pulse scheme generates an additional flip-angle dependent scaling to the traditional single-pulse excitation profile in such a way that the scaling is one when the flip-angle is ∼90° but becomes almost zero when the flip-angle is very small. Therefore, the background signals arising from the materials outside the sample coil experiencing a very small fraction of the RF flip-angles can be effectively suppressed. Various samples containing 1H and quadrupolar nuclei (17O, 25Mg, and 23Na) have been used to demonstrate the effectiveness of this newly proposed triple-pulse excitation in terms of suppressing the background signals and eliminating the acoustic ringing effects.

Customizable patterning and deformation of soft matter represents a powerful tool to achieve programmable 3D configurations of soft materials. However, customizing the multidimensional self-wrinkli...

Spider silks show unique combinations of strength, toughness, extensibility, and energy absorption. To date, it has been difficult to obtain spider silk-like mechanical properties using non-protein approaches. Here, we report on an artificial spider silk produced by the water-evaporation-induced self-assembly of hydrogel fibre made from polyacrylic acid and silica nanoparticles. The artificial spider silk consists of hierarchical core-sheath structured hydrogel fibres, which are reinforced by ion doping and twist insertion. The fibre exhibits a tensile strength of 895 MPa and a stretchability of 44.3%, achieving mechanical properties comparable to spider silk. The material also presents a high toughness of 370 MJ m−3 and a damping capacity of 95%. The hydrogel fibre shows only ~1/9 of the impact force of cotton yarn with negligible rebound when used for impact reduction applications. This work opens an avenue towards the fabrication of artificial spider silk with applications in kinetic energy buffering and shock-absorbing., Different models are believed to be the reason for the superior mechanical properties of spider silk. Here, the authors prepare artificial spider silk by water-evaporation-induced self-assembly of a hydrogel fibre made from polyacrylic acid and silica nanoparticles.

Hierarchically mesoporous titanosilicate single-crystalline nanospheres were synthesized by using a polyelectrolyte–surfactant mesomorphous complex templating method. The titanosilicate nanospheres...

Densely H-bonding assemblies are the key strategy found by nature to enhance the rupture strength of natural polymers without sacrificing their toughness, such as spider silk, while it still remains a great challenge using such intriguing strategy to prepare high-performance synthesized polymer or biopolymer enhanced polymer nanocomposites. To address this challenge, we report here a bio-inspired strategy using densely H-bonding assembly for facile fabrication of high performance polyurethane (PU) nanocomposites reinforced by hydroxyl-rich cellulose nanocrystals (CNCs) functionalized with 2-ureido-4-[1 H]-pyrimidinone motifs (CNC-UPy) containing self-complementary hydrogen bonds. These PU/CNC-UPy nanocomposites showed remarkably improved mechanical strength without sacrificing the elongation at break and toughness compared to pure PU matrix. Differential scanning calorimetry(DSC) results indicated that CNC-UPy could induce the formation of long range ordering of hard segment domains, due to the strong hydrogen bonding interactions between UPy motifs attached on CNC-UPy and PU matrix. Furthermore, wide angle X-ray diffraction (WAXD) measurements demonstrated that the strain-induced crystallization (SIC) was enhanced significantly by introducing CNC-UPy into PU, leading to a large stress at break. The enhanced interfacial H-bonding interactions between CNC and PU though UPy anchoring could overcome the inherent trade-off between the stiffness and toughness of polymer composites. The proposed bio-inspired strategy using densely H-bonding assembly will be with more extensive application prospects.

Polymeric materials combining good mechanical performances with self-healing ability and malleability have attracted dramatic attention, but it presently remains a challenge for the facile fabrication of such high-performance materials, not to mention the atomic-level characterization for understanding the molecular origin of the macroscopic properties. Herein, we proposed a facile strategy to fabricate a dual-cross-linked poly(n-butyl acrylate) polymer material, in which the self-complementary quadruple hydrogen bonding interactions between 2-ureido-4[1H]-pyrimidinone (UPy) dimers were utilized as the dynamic sacrificial cross-linkages, and thus to enhance the mechanical strength and toughness. The hydrogen bonding interactions between UPy dimers in such synthetic cross-linked polymer material were revealed in detail by selective saturation double-quantum (DQ) solid-state NMR spectroscopy under ultrafast magic-angle-spinning beyond 60 kHz. In the meantime, the self-healing capability and recyclability we...

Polyurethane elastomers have been widely used in the industry and daily life due to their versatile physical and chemical properties. Therefore, a fundamental understanding of the structures and dynamics at a molecular level will provide piercing insights into the precise design and application of new polyurethane materials. In this study, we mainly focused on investigating the strain-induced structural and dynamic changes in a typical polyurethane elastomer composed of poly(e-caprolactone) (PCL) and 4,4′-diphenylmethylene diisocyanate (MDI) as the soft and hard segments, respectively. Obvious strain-hardening phenomenon was observed during the mechanical tensile test, and a systematic comparison was performed on the fractured and pristine samples. DSC results revealed that the crystallization of PCL chains was still going on after the sample was fractured, and the crystallite structures became stable after physical aging at 25 °C for two days. 1H solid-state nuclear magnetic resonance (NMR) experiment was further employed to determine the fraction of mobile PCL chains that were converted to crystallites during stretching. Besides, the microphase separation was also significantly enhanced in the fractured sample. The mobility of amorphous PCL chains was largely reduced due to the strain-induced crystallization of nearby PCL segments, as revealed by the 1H magic-sandwich echo (MSE) NMR experiments. 1H multiple quantum (MQ) NMR experiments also quantitatively revealed the strain-induced orientation of amorphous PCL chains in the fractured sample, indicating that the PCL crystallites were acting as the physical cross-linkages to prevent the contraction of the elongated PCL chains when the sample is fractured.

Polymeric antifogging and frost-resisting coatings were successfully prepared, but the performances of amphiphilic coatings containing different kinds of cationic, zwitterionic and anionic polyelectrolytes are still needed to investigate systematically. In this work, antifogging/frost-resisting coatings with high transparence were developed from amphiphilic copolymers of cationic, zwitterionic or anionic poly(2-(dimethylamino)ethyl methacrylate (DMAEMA)-co-2,2,2-trifluoroethyl methacrylate (FMA))-b-polyelectrolytes with a small amount of ethylene glycol dimethacrylate via UV-curing. Studies on the prepared amphiphilic coatings suggested that the cationic and zwitterionic coatings exhibited superior antifogging properties, whereas the anionic polyelectrolyte-based coating demonstrated a better frost-resisting behavior. Water molecule activities in the amphiphilic coatings were analyzed by differential scanning calorimetry, Raman spectroscopy and low field nuclear magnetic resonance. It was found that the cationic and zwitterionic coatings containing 2-(methacryloyloxy)-ethyltrimethyl ammonium chloride and sulfobetaine methacrylate, respectively, exhibited stronger polymer-water interactions dominated by strong hydrogen bonds, and held more nonfreezable water content with shorter transverse spin-spin relaxation time T2 than the anionic coating containing 3-sulfopropyl methacrylate potassium (SPMA). Electrostatic interactions between anionic SPMA and DMAEMA units in the copolymer could weaken the polymer-water interaction, leading to a compromise in the antifogging performance and an enhancement of frost-resisting ability of the coating. The results of this study would be applicable for exploring the advanced antifogging/frost-resisting coatings.

Hierarchically porous silica KIT-6 and SBA-15 mesostructures were successfully synthesized by using a mesomorphous complex of a nonionic triblock copolymer (pluronic P123) and an anionic polyelectrolyte (polyacrylic acid) as the dynamic template. The obtained mesoporous silica materials possessed both ordered mesopores (∼7 nm) and nanopores (∼15-50 nm), and the long-range order of the mesophase was not perturbed by the embedded larger secondary nanopores. Moreover, hierarchically porous silica KIT-6 exhibited enhanced adsorption capacity in enzyme and protein immobilization, which was attributed to the hierarchically porous structure.

Inspired by the nature material, a crosslinked network structure of polyurethane/epoxy resin composite material was built through Diels-Alder (DA) reversible covalent bond reaction between the dienes and dienophile group on the side chain of epoxy resin and polyurethane respectively. The synthesized composite material combined the advantages of polyurethane and epoxy resin. The hard segments of polyurethane and epoxy resin were closely combined through the DA reaction and high density hydrogen bonding. The strength, hardness and toughness of the composite material were greatly enhanced. DA covalent bonds can be reversible with varying the temperature, which led to the heat reprocessing ability of the synthesized composite material. The well-established structure-property relationship shown in this paper could further provide guidance for fabrication of high performance recyclable material with precisely controllable microstructures and behaviors.

Polyurethane materials (PUs) have been widely used in industry and daily life due to the versatile chemistry. However, despite the rapid advance in synthetic chemistry, it still remains a significant challenge for the facile fabrication of PUs with a single cross-linked network embedded with excellent mechanical properties and recyclability. Herein, in this study, we proposed a simple strategy to fabricate a high-performance recyclable cross-linked PU and revealed the relationship between microscopic structure and macroscopic properties. The UPy (2-ureido-4-[1H]-pyrimidione) motifs were incorporated into the backbone chains of PUs, where the quadruple hydrogen bonding interactions between UPy dimers can significantly enhance the mechanical strength and toughness. Furthermore, a single small molecular Diels-Alder adduct was utilized as the chemical crosslinker, rendering the final cross-linked PUs healable and recyclable. The thermal reversibility of the Diels-Alder reaction was well verified by DSC and solid-state NMR spectroscopy. Notably, it was found that the incorporation of UPy motifs could enhance the strain-induced crystallization (SIC), leading to a large stress at break. The structural and dynamic changes induced by SIC were quantitatively addressed by proton multiple-quantum NMR spectroscopy and SAXS experiments, where SIC further imposed restrictions on the mobility of surrounding polymer chains in the soft domain and led to the change of microphase separated nanostructures. Overall, a simple strategy is proposed here for the facile fabrication of high performance recyclable PUs, and the detailed investigation here on the structure-property relationship may further provide insights into developing high performance polymeric materials.

Hydrogels have received considerable attention as an innovative material due to their widespread applications in various fields. As a soft and wet material, its mechanical behavior is best understood in terms of the viscoelastic response to the periodic deformation, which is closely related to the microscopic chemically/physically cross-linked structures. Herein, a dual-cross-linked (DC) hydrogel, where a physically cross-linked network by ionic coordination (Fe3+) is imposed on a chemically cross-linked poly(acrylamide-co-acrylic acid) network, was studied in detail by rheology and proton multiple-quantum (MQ) NMR spectroscopy. Rheology experiments revealed the diverse temperature- and strain-frequency-dependent viscoelastic behaviors for DC hydrogels induced by the dynamic Fe3+ coordination interactions, in contrast to the single chemically cross-linked (SC) hydrogels. During the shear experiment, the trivalent Fe3+ complex with moderate/weak binding strength might transform to those with strong binding...

The change in the infrared spectrum of polymer samples with temperature and their differential scanning calorimetry (DSC) experimental results are analyzed. According to the van't Hoff equation at constant pressure, the changes in the absorbance ratio corresponding to high and low vibrational states are calculated, and the apparent enthalpy differences of the vibration energy states transformation of the characteristic group can be obtained. From the experimental results, we can find that characteristic vibration modes of a chemical group in a polymer are under the influence of the glass transition process of the polymer with a different extent. The characteristic vibration modes of the same chemical group behave differently due to the influence of the polymer system at which the chemical moiety is situated.

Multicompartment block copolymer nanoparticles (MCBNs) constructed with a thermo-responsive and base-sensitive poly(N-acryloylsarcosine methyl ester)-block-polystyrene (PNASME-b-PS) and a pH-responsive poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) are synthesized by dispersion RAFT polymerization employing two macro-RAFT agents. These MCBNs contain a hydrophobic polystyrene (PS) core and dispersed microdomains formed either by the pH-responsive poly(4-vinylpyridine) (P4VP) and/or the thermo-responsive and base-sensitive poly(N-acryloylsarcosine methyl ester) (PNASME). By changing the polymerization degree of the PS block, the molar ratio of two diblock copolymers, temperature, pH, and tuning the interaction between the acidic poly(N-acryloylsarcosine) block obtained from hydrolysis of PNASME and the alkaline P4VP block, convenient tuning of the size and morphology of the MCBNs is achieved, and well-defined block copolymer nanoparticles including several MCBNs with different microdomains, core–corona particles and shell-bonded core–shell nanoparticles have been prepared.