Cross-linked Network Structure Research Articles

P/N/Si-rich and flexible coating imparting polypropylene excellent flame retardancy without compromising its inherent mechanical properties

In general, the addition of flame retardants may lead to the degradation of the mechanical properties of polymers, despite enhancing their flame retardancy. However, flame-retardant coatings have the potential to provide good flame resistance to polymers without compromising their inherent mechanical properties. In this study, we applied highly adhesive and flexible polysiloxane flame-retardant coatings (196 μm) to polypropylene, resulting in reductions of 74.9 %, 58.0 %, 80.0 %, and 56.4 % in peak heat release rate, peak smoke production rate, fire growth rate, and mass loss, respectively. By incorporating the lab-synthesized DOPO-modified polysiloxane (APID), the flame-retardant efficiency of ammonium polyphosphate (APP) was greatly enhanced. The primary film-forming agent, (3-aminopropyl) triethoxysilane (APTES), played a key role in maintaining the compatibility of APP and APID with the coating, as well as facilitating the formation of a robust SiOSi crosslinked network structure that strengthened the resulting char layer. The interactivity between the various components, including hydrogen bonds and crosslinked network structures, contributed to improved uniformity, thermal stability, and adhesion of the coatings. Moreover, the coatings exhibited resistance to ultraviolet radiation and water. Our findings suggest that highly flexible and adhesive flame-retardant coatings hold significant potential for applications in polymer protection. These promising results provide a viable pathway for improving the fire protection of polymers through the use of high-adhesive intumescent flame-retardant coatings.

Effect of inorganic material surface chemistry on structures and fracture behaviours of epoxy resin

The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and silicon substrates with varying surface chemistries (OH and H terminations) with a smoothness below 1 nm, which have different adhesive strengths by ~13 %. The epoxy resins within sub-nanometre distance from the surfaces with different chemistries exhibit distinct amine-to-epoxy ratios, cross-linked network structures, and adhesion energies. The OH- and H-terminated interfaces exhibit cohesive failure and interfacial delamination, respectively. The substrate surface chemistry impacts the cross-linked structures of the epoxy resins within several nanometres of the interfaces and the adsorption structures of molecules at the interfaces, which result in different fracture behaviours and adhesive strengths.

MXene-mediated Interfacial Growth of 2D-2D Heterostructured Nanomaterials as Cathodes for Zn-based Aqueous Batteries.

In this study, we introduce a novel approach for synthesizing two-dimensional (2D) MXene heterostructures featuring a sandwiched and cross-linked network structure. This method addresses the common issue of activity degradation in 2D nanomaterials caused by inevitable aggregation. By utilizing the distinct surface characteristics of MXene, we successfully induced the growth of various 2D nanomaterials on MXene substrates. This strategy effectively mitigates self-stacking defects and augments the exposure of surface areas. In particular, the obtained 2D-2D MXene@NiCo-layered double hydroxide (MH-NiCo) heterostructures exhibit enhanced structural stability, improved chemical reversibility, and heightened charge transfer efficiency, outperforming pure NiCo LDH. The aqueous MH-Ni4Co1//Zn@carbon cloth (MH-Ni4Co1//Zn@CC) battery demonstrates exceptional performance with a remarkable specific capacity of 0.61 mAh cm-2, maintaining 96.6 % capacitance after 2300 cycles. Additionally, it achieves an energy density of 1.047 mWh cm-2 and a power density of 32.899 mW cm-2. This research not only paves the way for new design paradigms in energy-related nanomaterials but also offers invaluable insights for the application and optimization of 2D-2D heterostructures in advanced electrochemical devices.

Boosting the acid penetration barrier of epoxy-silica organic-inorganic hybrid coating via adjusting its molecular structures: Experimental and molecular dynamics simulation study

The permeability barrier property of coatings against corrosive media determines their service life. Herein, the molecular structure of epoxy-silica organic-inorganic hybrid (OIH) coating is regulated to endow the coatings with enhanced barrier properties by a simple sol-gel method. Experiments show that the coating with 8% Si-O-Si structure has the best acid penetration resistance after 45 days of immersion in 10 wt.% H2SO4 solution. In addition, molecular dynamics simulation results show that the molecular structure of OIH affects the densification of the coating, forming a highly cross-linked network structure that inhibits the diffusion and destructive effects of corrosive media and thus affects the acid penetration resistance of the coating.

Influence of vinyl polyhedral oligomeric silsesquioxane with different functionalities and cage structures on the mechanical properties and ablation resistance of EPDM composites

AbstractFour vinyl polyhedral oligomeric silsesquioxane (POSS) with different functionalities and cage structures, monovinyl‐POSS (monov‐POSS), divinyl‐POSS (div‐POSS), trivinyl‐POSS (triv‐POSS), and tetravinyl‐POSS (tetrav‐POSS) were prepared and blended into fiber‐reinforced ethylene propylene diene monomer (EPDM—EPDM/AF) in the form of chemical cross‐linking to obtain four modified composites with various cross‐linked network structures and cage structures to investigate the influences and improvement of cross‐linking network and cage structures on the mechanical, thermal stability and ablation resistance of EPDM/AF. The results showed that the POSS of multi‐functionality with small steric hindrance, such as tetrafunctional tetrav‐POSS, can most significantly improve mechanical properties of EPDM/AF by forming denser crosslinking network structures, and the tensile strength and elongation at break of EPDM/AF/tetrav‐POSS can be increased 73.3% and 42.1% compared with EPDM/AF, respectively. POSS that has a complete cage structure and enables the modified composites to obtain a relatively dense cross‐linked network structure, such as difunctional div‐POSS can more substantially enhance the thermal stability and ablative resistance of EPDM/AF with the LAR and MAR of EPDM/AF/div‐POSS reduced by 25.2% and 10.5% compared to EPDM/AF, respectively. High‐temperature thermal transition of four modified composites at gradient temperatures was investigated to explain the relationship between the structure of POSS and ablation properties.Highlights Four POSS with different functionalities and cage structures were designed. Mechanical and ablative properties were reinforced by four vinyl POSS. Multifunctional POSS can most significantly improve mechanical properties. Functionality and cage structure together influence ablative property. High‐temperature thermal transition of modified composites was investigated

Fabrication of elastic SiO2 aerogels with prominent mechanical strength and stability reinforced by SiO2 nanofibers and polyurethane for oil adsorption

The separation of oil from wastewater and materials for oil absorption are highly demanded in the modern industrialization. For these purposes, silica aerogels with high hydrophobicity and surface aera and low density are promising candidates for oil absorption, but limited by the poor mechanical strength and structure stability during the usage. In this study, we presented a novel compressive silica aerogel by silica nanofiber (SNF) reinforcement and subsequent hydrophobic polyurethane strengthening via moisture curing (PSAG). The obtained PSAG exhibits unique core/shell fibrous reinforcement and prominent crosslinked network structure. The porous PSAG has a porosity of 81.06 % and density of 0.43 g cm−3 at solid content of 20 %. The hydrophobic PSAG shows an impressive sorption capacity towards CH2Cl2 (11.2 g g−1), THF (5.5 g g−1) and acetone (3.8 g g−1), being able to separate 100 % of oils from an immiscible oil–water mixture. The PSAG shows exceptional resistance to acidic and alkaline conditions and has high flexibility and desirable reusability in repeatedly oil adsorption. Most importantly, the mechanical strength of SAG can be improved to 0.27 MPa of PSAG at prepolymer solid content of 20 %, and no cracking or deformation were observed after 50 cycles. Additionally, the PSAG shows impressive thermal insulation and flame retardancy performance in the air, which should have potential application as insulator for the solar evaporation for the purification of wastewater. This work provides new understanding and insight for further design and optimization of polyurethane-based reinforced aerogels.

Construction and tribological properties of poly acrylic acid‐poly(3‐(methacryloylamino)propyl) dimethyl(3‐sulfopropyl)ammonium hydroxide hydrogel coatings embedded with SiO2 nanoparticles on Ti6Al4V substrate

AbstractThe development of highly effective bio‐lubricant coatings for arthritis treatment is extremely demanded. Herein, inspired by the efficient lubrication of articular cartilage, acrylic acid (AA) with (3‐(methacryloylamino) propyl) dimethyl (3‐sulfopropyl) ammonium hydroxide (MPDSAH) hydrogel coatings containing nanoparticles on Ti6Al4V substrate were designed and fabricated via UV grafting technology. SiO2 and SiO2 grafted with PAA polymer brushes (SiO2‐g‐PAA) were separately doped into the PAA‐PMPDSAH hydrogel. The PAA‐PMPDSAH/SiO2‐g‐PAA exhibits good tensile and compressive properties compared with PAA‐PMPDSAH/SiO2 hydrogel, with an enhancement of 183.4% in tensile modulus and 60.8% in compressive modulus. The PAA‐PMPDSAH/SiO2‐g‐PAA hydrogel coatings exhibit a low wear volume, 2.9 ± 0.16 × 106 μm3, representing a decline of 32.1% and 61.3% compared with the PAA‐PMPDSAH and PAA‐PMPDSAH/SiO2 hydrogel coatings, respectively. The antiwear performance has obviously improved. The hydrophilic PAA polymer brushes prevent the agglomeration of nanoparticles and promote homogeneously dispersion within the hydrogel. The three‐dimensional crosslinked network structure of hydrogel effectively protects the structural integrity of the polymer brushes, thereby facilitating enduring lubrication properties. This work provides a strategy for promising artificial joint lubrication in biomedical fields.

Vanillin-derived epoxy-coated flexible cellulose nanofiber film for multifunctionality and energy harvesting applications

Cellulose nanofiber (CNF), a state-of-the-art sustainable material, often suffers from high hydrophilicity, flammability, and emaciated UV-blocking properties, hampering its broad growth in high-performance applications. This paper reports a novel multifunctional bio-based-epoxy-coated CNF film promising to cope with the addressed challenges. Key to this approach is the etherification reaction, which favors excellent compatibility between CNF film and vanillin-derived epoxy (VDE) resin, resulting in a robust crosslinked network structure with a remarkable adhesion strength (16.12 ± 0.7 MPa), tensile strength (211.6 ± 7.2 MPa), and Young's modulus (8.6 ± 0.4 GPa). A thin VDE layer coating on CNF (VDE/CNF) film significantly presented the film's hydrophobicity of around ⁓93.0 ± 1.5° and UV shielding performance of ⁓100%. Additionally, the coated VDE/CNF film exhibited higher thermal stability (213 °C) and char residue (36%) than the CNF film. Most importantly, despite the high flammability nature of CNF film, the VDE/CNF film passed a V-0 rating under the UL-94 test with a limited oxygen index of 31.8%. The VDE/CNF film was utilized for a triboelectric nanogenerator (TENG) to demonstrate its broad technological impact. Notably, the VDE/CNF-TENG exhibited a significant output power of 18.33 μW. This critical approach offers a promising way to extensively utilize sustainable and multifunctional VDE/CNF nanocomposite materials for high-performance applications.

Solution-recrystallization mechanism of g-C3N4 and its inhibitory effect on polysulfide shuttling through cross-linked porous network structure with carbon nanotubes

Lithium-sulfur batteries have the advantages of high specific capacitance density and high theoretical capacity, which are attracting more and more attention in the field of energy storage. However, in practice, there are still many difficulties, such as the poor conductivity of sulfur, the large volume expansion of sulfur, and the shuttle effect of polysulfides, which lead to rapid capacity degradation and poor cycling stability. Here, we utilize g-C3N4 which is soluble in concentrated H2SO4 and has a good solution-recrystallization reversible property, alcohol was used as deprotonation solvent, the g-C3N4/CNT composites were prepared by the method of solution-recrystallization as sulfur host. The dissolution and precipitation mechanism of g-C3N4 in concentrated sulfuric acid and the composite mechanism with CNT were revealed. The g-C3N4/CNT/S cathode exhibit excellent electrochemical properties. The capacity of SPCNT11 can still be maintained to 1013 mAh·g−1 after 200 cycles at 0.2 C, with a capacity retention rate of 73.2%. Even at rate of 4C, the SPCNT11 material still has a capacity of 547 mAh·g−1 after 450 cycles. The first-principle calculation results further reveal that the interaction between g-C3N4 and CNT produces conjugated effect, the constrain of g-C3N4 to electrons is weakened, enhances its conductivity, and thus realizes the effect of promoting polysulfide transformation.

Investigation on One-Component Waterborne Epoxy Emulsified Asphalt (OWEEA) Used as Bonding Material

Due to the issue of weakened adhesion between ultra-thin surface overlays, higher demands have been placed on bonding layer materials in practical engineering. This study proposed a method for preparing a one-component waterborne epoxy resin-modified emulsified asphalt (OWEEA) and explored the impact of different ratios on its performance. The basic physical and mechanical properties of the OWEEA, as well as its rheological characteristics, were investigated through penetration tests, softening point tests, ductility tests, tensile tests, and dynamic shear rheological tests. Pull-out tests and shear tests considering different substrates were used to evaluate the interfacial bonding performance of the OWEEA as a bonding layer material, and comparative analysis was conducted with conventional waterborne epoxy resin-modified emulsified asphalt. Based on microscopic testing and analysis, the laws of physical and chemical changes and secondary curing characteristics of the one-component waterborne epoxy emulsion (OWE) during the modification of emulsified asphalt were elucidated. The results indicated that the OWE prepared in this study significantly enhanced the tensile strength and bonding properties of emulsified asphalt. The results showed that the tensile strength, bonding strength, and shear strength of the OWEEA increased from 0.15 MPa, 0.36 MPa, and 0.35 MPa to 0.55 MPa, 1.29 MPa, and 2.01 MPa, respectively. The modification effect of the OWEEA surpassed that of conventional waterborne epoxy emulsion, albeit with a certain reduction in elongation at break, reduced from 1551% to 98%. Furthermore, the OWEEA showed a distinct secondary curing phenomenon. The results of the SEM tests showed that high temperatures accelerated the formation of the crosslinked network structure of OWE, promoting its integration with emulsified asphalt and resulting in a more uniform and dense structure, significantly enhancing bonding strength in a short period. In the actual road construction process, laying hot-mix asphalt mixtures on the bonding layer can further enhance its curing effect and improve its bonding performance.

Cross-Linking Methods of the Silk Protein Hydrogel in Oral and Craniomaxillofacial Tissue Regeneration.

Craniomaxillofacial tissue defects are clinical defects involving craniomaxillofacial and oral soft and hard tissues. They are characterized by defect-shaped irregularities, bacterial and inflammatory environments, and the need for functional recovery. Conventional clinical treatments are currently unable to achieve regeneration of high-quality oral craniomaxillofacial tissue. As a natural biomaterial, silk fibroin (SF) has been widely studied in biomedicine and has broad prospects for use in tissue regeneration. Hydrogels made of SF showed excellent water retention, biocompatibility, safety and the ability to combine with other materials. To gain an in-depth understanding of the current development of SF, this article reviews the structure, preparation and application prospects in oral and craniomaxillofacial tissue regenerative medicine. It first briefly introduces the structure of SF and then summarizes the principles, advantages and disadvantages of the different cross-linking methods (physical cross-linking, chemical cross-linking and double network structure) of SF. Finally, the existing research on the use of SF in tissue engineering and the prospects of using SF with different cross-linking methods in oral and craniomaxillofacial tissue regeneration are also discussed. This review is intended to show the advantages of SF hydrogels in tissue engineering and provides theoretical support for establishing novel and viable silk protein hydrogels for regeneration.

Tea pomace protein-ε-polylysine-anthocyanin composite nanocomplexes: Elucidation of stability, structural properties, and in vitro digestion

Nano-complexation with food proteins has been well recognized to be an effective and safe strategy to improve stability and bioavailability of bioactive compounds. In this study, we applied tea pomace protein (TP) and ε-polylysine (PLL) to load anthocyanins (ACNs), which were further characterized by scanning electron microscopy (SEM), fourier transformed infrared spectroscopy (FTIR), and fluorescence spectrum (FS). The stability and digestive characteristics in vitro were also investigated. The result showed that ACNs-loaded TP-PLL nanocomplexes (TPPLA) formed a dense three-dimension crosslinked network structure by interactions between TP and PLL, while the flakes of ACNs were dispersed in the grid. The interactions between nanocomplexes were analyzed by molecular docking and found to be mainly through hydrogen bonds on polyphenols (C3G) or electrostatic interactions in the hydrophobic cavities of TP (11 S). Compared with free ACNs, The TPPLA nanocomplexes improved its encapsulation efficiency (63.63 ± 0.50 %) and thermal retention rate (70.18 ± 0.98 %). And they presented excellent properties of controlled release during the simulated digestion in vitro. This study is the first to propose developing and utilizing tea pomace protein as a microencapsulated material and the result may promote the successful application of TPPLA nanocomplexes in foods and nutraceuticals.

Improving the ohmic polarization of high-temperature proton exchange membrane fuel cells using crosslinked polybenzimidazole membranes containing acidophilic quaternary ammonium groups synthesized by one-step strategy

Ingenious crosslinked network structure in phosphoric-acid-doped polybenzimidazole membranes can mitigate the mutual restriction of proton conductivity and mechanical properties. However, the complicated synthesis of tailored macromolecular crosslinker and the time-consuming post-treatment hinder their practical application as high-temperature proton exchange membranes. Herein, crosslinked polybenzimidazole membranes are synthesized using small molecular crosslinkers containing acidophilic quaternary ammonium groups through a one-step crosslinking strategy. After doping with phosphoric acid, the quaternary ammonium-biphosphate ion-pair coordination and the crosslinked structure result in the improved anhydrous proton conductivity, oxidation stability, and mechanical strength of the formed membranes compared to the sample without the crosslinking structure. A membrane with the optimized degree of crosslinking exhibits an anhydrous conductivity of 72.27 mS/cm at 160 °C, with a tensile strength of 12.14 MPa. Benefiting from the crosslinked structure and high proton conductivity, the accordingly formed membrane electrode assembly possesses a high open-circuit voltage of 1.01 V and animproved ohmic polarization, delivering a peak power density of 0.66 W/cm2 using hydrogen as fuel and air as oxidant.

A facile method to prepare biobased flexible polydimethylsiloxane − Benzoxazine resin: Dielectric properties and high heat resistance

For the benefit of meet the industrial demand of integrated circuits for low dielectric constant (k) and the environmental requirements of sustainable development, it is important to prepare biobased benzoxazine resin with low k and high heat resistance by solvent-free method. In this paper, the biobased monomer V-fa containing aldehyde group was synthesized by biobased raw materials furfurylamine and vanillin, and then reacted with amino-terminated polydimethylsiloxane (PDMS) to prepare benzoxazine monomer V-fa-pdms containing schiff base structure by a solvent-free method. Then, the monomer was cured to obtain biobased benzoxazine resin poly(V-fa-pdms), and the heat resistance, mechanical and dielectric properties of poly(V-fa-pdms) were studied. The results indicate that the resin exhibits excellent thermal stability and toughness by combining benzoxazine and PDMS reasonably. The initial thermal decomposition temperature (Tdi, 5% thermogravimetric loss) is 387 °C, and the material also exhibits excellent dielectric properties. When the frequency increases from 1 Hz to 1 MHz, the k of the material decreases from 2.71 to 2.60, and the fluctuation range of dielectric loss is 0.0051–0.0049. With the increase of frequency, both k and dielectric loss show a downward trend. At the same time, the material shows good corrosion resistance in commonly used solvents. These excellent properties of poly(V-fa-pdms) are due to the existence of a high cross-linked network structure formed by multiple cross-linking sites in the polymer network and the combined effect of low k and high heat-resistant PDMS components.

A multi-purpose adhesive with high strength and bond sensitive stress sensing

Despite the important roles of pressure-sensitive adhesives (PSA) and hot-melt adhesives (HMA) in wood furniture, aerospace, and other fields, the inherent contradiction between them owing to their different molecular mechanisms remains a great challenge in developing high-performance, multi-purpose adhesives. In this study, butylphenyl crosslinked polymers were constructed to overcome the intrinsic contradiction between PSA and HMA and to develop a multi-purpose adhesive. The formation of electrostatic interactions and hydrogen bonding networks between inter/intramolecular functional groups gave PSA excellent adhesive strength (3.0 MPa) and peel strength (4.7 N/cm) at light pressures of 0.3 MPa. Interestingly, PSA has the ability to achieve repeatable bonding performance at the gluing interface and excellent underwater bonding performance owing to its special crosslinked network structure consisting of long alkane chains and the synergistic effect of fillers (rosin and nano-silica). Multifunctionalities, such as heterointerfacial adhesion, rapid bonding, reuse, interfacial debonding, and container leakage repair, have been achieved.

Biocompatible polyurethanes with thermally-induced shape memory properties derived from three-arm branched poly(ε-caprolactone-co-γ-butyrolactone)-b-poly(lactide) block copolymers

A series of poly(lactide)-based polyurethanes with cross-linked network structure was synthesized through the chain extension of three-arm branched poly(ε-caprolactone-co-γ-butyrolactone)-b-poly(lactide) (3PBCL-b-PLA) block copolymers with various molecular weights and optical activities of PLA blocks. The structure of the synthesized poly(lactide)-based polyurethanes was analyzed, and it was confirmed that they contained the cross-linked network structure. Effects of the molecular weight and optical activity of PLA block on the various properties such as crystallization, mechanical property, shape memory performance, thermal stability and hydration ability were discussed. By simultaneously adjusting the molecular weight and optical activity of PLA blocks, the crystallization of flexible PCBL blocks and rigid PLA blocks in the synthesized cross-linked polyurethanes was effectively controlled, which was the basis for constructing poly(lactide)-based polyurethanes with a broad ranged mechanical property, excellent shape memory properties and controllable hydration ability. The synthesized polyurethanes exhibited adjusted tensile strength and elongation at break in the range of 11.2–32.4 MPa and 41–753 %, with the water content varying from 1.1 % to 20.1 %, respectively. The shape fixity ratio and shape recovery ratio of L-PU2.9 could reach 90.9 % and 96.0 %, respectively. The effect of stereocomplex-crystallization on the properties of poly(lactide)-based polyurethane was also analyzed. Stereocomplexed polyurethane based on 3PCL-b-PLA block copolymer enantiomers with short PLA block was constructed, which achieves fully stereocomplexation in a wide mixing ratio (20–50 %). It was found that the formation of a small number of stereocomplex-crystals can change the properties of poly(lactide)-based polyurethane in a wide range. Eventually, it was demonstrated by in vitro hemolysis test, cytotoxicity test and live/death staining that the synthetic poly(lactide)-based polyurethanes exhibited excellent biocompatibility. These results suggested that these biocompatible shape memory poly(lactide)-based polyurethanes with tunable mechanical properties and hydration ability demonstrated the promising potential as an excellent implantation for biomedical application.

Geometry-based cross-linking algorithm for modeling resorcinol resins through united-atom molecular dynamics simulations

The addition-condensation polymerization (ACP) of resorcinol with formaldehyde and the electrochemical polymerization (ECP) of resorcinol were desirable to improve the performances of resins. To achieve computational design, a new geometry-based cross-linking modeling algorithm for three-dimensional (3D) cross-linked network structures of resorcinol resins was developed for molecular dynamics (MD) simulations using a united-atom model. The ACP and ECP of resorcinol were successfully modeled using one algorithm by changing the parameters of the reaction rate constants of methylene, ether, and biphenyl bond formations. Furthermore, reaction judgment was performed under a reaction probability function comprising the Gaussian functions based on the interatomic distance of the reaction candidate atom pairs and interior angles regarding the spatial arrangement of two resorcinol rings. This geometry-based cross-linking algorithm successfully generated strainless 3D cross-linked network structures of the ACP and ECP resorcinol resins without the formation of highly bent unstable structures, such as U-shaped biphenyls. The MD simulation results indicated that the cross-linking of the ACP resin comprising methylene linkages proceeded with a network structure formation mechanism similar to that of phenolic resins, where the cross-linked network structure was determined at the gel point and the reactions after the gel point were to fix and freeze the network structure. For the ECP resins comprising ether and biphenyl linkages, the molar ratio of ether to biphenyl bonds affected the elastic property of the resins, and the incorporation of rigid biphenyl structures into ether-linkage networks increased the elastic modulus. Moreover, an increase in rigidity was observed as a decrease in the Poisson's ratio.

Integrating with a tough framework and efficient self-healing behavior based on a flexible polymer skeleton for Si anode binders in lithium-ion cells

As a prospective and efficient strategy to address the volume expansion of the Si nanoparticles, the binder plays an increasingly significant role in the Si anode of lithium-ion batteries. Based on the inspiration of natural physics and cross-linked networks, a functional (named polyacrylic acid-citric acid-polyethyleneimine) binder that is similar to a flexible polymer skeleton integrated with a tough framework and efficient self-healing behavior is designed to achieve long cycling stability for Si anodes. The cross-linked network can be stabilized by the amide bonds, formed by polyethyleneimine (PEI) and polyacrylic acid (PAA). Based on this, citric acid (CA) can be added to form multiple hydrogen bonds, whose carboxyl groups can also establish a more reversible cross-linked network with Si particles. Then, PEI and CA molecules can connect with PAA to form a “rigid and flexible” structure. The expansion stress of Si nanoparticles is relieved by the protective buffer layer built by the addition of PEI and CA molecules. In addition, PAA, PEI, and CA work together to solve the problem that the action of CA and PAA alone cannot perform well under large currents. Hence, this water-based binder with a three-dimensional cross-linked network structure with self-healing ability has better performance during cycling: at a current density of 0.2C, it still has a capacity of 2017.4 mAh·g−1 after 200 cycles, with a capacity retention rate of 80.7 % (1745.3 mAh·g−1, 300 cycles, a capacity retention of 74.9 %).

Low hydrogen permeability and high durability proton exchange membrane with three-dimensional acid-base crosslink structure for water electrolysis

Introducing a acid–base cross-linked network structure and reinforcement layer into a proton exchange membrane (PEM) can effectively improve its performance, durability, and hydrogen permeability for high-pressure PEM water electrolysis (PEMWE). Here, a hyperbranched polymer containing imidazole terminal groups (HBP-MZ) is designed and prepared, then is used to form a novel PEM possessing a cross-linked network structure consisting of HBP-MZ, perfluorosulfonic acid (PFSA) and reinforced with a poly(ether-ether-ketone) (PEEK) mesh. The microstructure of the PEM is characterized using thermal performance analysis. Benefiting from the acid–base crosslinked structure, the obtained PEM has a more compact structure, induces a drastic increase in dimensional stability, mechanical properties, proton conductivity and stability in water. The HBP-MZ/PFSA@PEEK membrane exhibits excellent water electrolysis performance, low high-frequency impedance, and superior stability: the HBP-MZ/PFSA@PEEK membrane provides an electrolytic performance of up to 1.76 V at 2.0 A cm−2 and 1.84 V at 3.0A cm−2 (60 °C, with an IrO2 loading of 1.0 mg cm−2), and exhibits a 6.2 μV h−1 average voltage degradation rate during durability testing. Benefiting from the characteristics of HBP and the existing cross-linked structures, the obtained HBP-MZ/PFSA@PEEK membrane exhibits a lower hydrogen crossover current density of 1.06 mA cm−2 and maintains a lower hydrogen content in oxygen under conditions of high current density and high pressure. This work provides a promising way to prepare a PEM with high durability and low gas permeability that could be applied in high-pressure water electrolysis.

Microporous and functional group Co-designed polyesteramide membranes for efficient and broad-spectrum organic solvent nanofiltration

Organic solvent nanofiltration (OSN) is an emerging energy-efficient separations technology, which urgently requires easily processable OSN membranes with high selectivity and broad-spectrum organic solvent applicability to facilitate enhanced industrial applications. Herein, we describe the preparation of microporous polyesteramide (PEA) membranes through interfacial polymerization (IP) between amino-diphenol monomers and trimesoyl chloride (TMC) on a poly(ether ether ketone) (PEEK) support. The crosslinked network structures and large twisted monomers enhance the microporosity of PEA membranes, leading to a significant improvement in solvent permeance while maintaining high selectivity. The optimized PEA membrane demonstrates exceptional permeance for acetone (21.0 ​L ​m−2 ​h−1 bar−1) and methanol (14.3 ​L ​m−2 ​h−1·bar−1), with a molecular weight cut-off of 296 ​g ​mol−1. Additionally, the PEA/APH-diphenol membrane exhibits ultrafast permeance for the nonpolar solvent toluene (8.3 ​L ​m−2 ​h−1·bar−1), owing to the introduction of a large number of ester groups. Overall, PEA membranes prepared through the molecular-level structure design of IP monomers possess enormous industrial application potential owing to their high performance and broad-spectrum applications.