Cross-linked Network Structure Research Articles

An eco-friendly strategy of cell wall stapling: In situ crosslinking of acrylic acid emulsion impregnated in thermally treated poplar wood

Traditional wood modification methods often result in the release of harmful substances and energy wastage. This study proposes an efficient and environmentally friendly modification strategy for fast-growing poplar wood. The approach involves polymerizing organic linear molecules within the cell wall to form stitches, thereby enhancing the dimensional stability and mechanical properties of wood and increasing its ability to withstand various environments. Poplar wood specimens were treated via a method that combines heat treatment with acrylic emulsion impregnation. The research findings indicated an improvement in the mechanical properties of poplar wood following the combined treatment. Moreover, poplar wood subjected to this treatment approach exhibited a 35.24 % lower water absorption rate after a 7-day water immersion test, and tangential and radial swelling rates of the wood were reduced by 29.66 % and 45.68 %, respectively. Scanning electron microscopy revealed excellent penetration of acrylic emulsion into wood cells; the emulsion infiltrated the wood and adhered to the cell walls, forming a crosslinked network structure. Analysis of the modification mechanism through X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy showed that the successful infusion of acrylic emulsion compensated for the lower mechanical properties of thermally treated wood, thus improving the utilization value of poplar. The acrylic emulsion is an environmentally friendly and harmless modifier, making the modified wood suitable for various applications, including indoor furniture, logistics, and outdoor facilities. This modification strategy enables efficient resource utilization and provides valuable insights for the sustainable development of the timber industry.

Prediction and investigation of water repeated absorption and release properties of superabsorbent polymers during the dry-wet cycles in different solutions

Superabsorbent polymers (SAP) with a three-dimensional cross-linked network structure are used in the concrete field due to their good water absorption and water retention properties. The changes of its repeated water absorption and release properties have an important impact on crack healing, but there is still a lack of relevant research. This study mainly uses the tea-bag method to explore the repeated water absorption and release behavior of sodium polyacrylate and polyacrylic acid-acrylamide copolymers in deionized water, cement filtrate, and saturated calcium hydroxide solution. The quantitative analysis of the change in the peak area of the water-absorbing functional group was performed by fourier transform infrared spectroscopy. The morphology and elements of SAP under different dry-wet cycles were analyzed by scanning electron microscope-energy spectrum analysis. The repeated swelling behavior of SAP was predicted using the classical models. The results showed that the repeated water absorption performance of SAP gradually decreased with the increase of the number of wet-dry cycles. The slope of the curve for the second-order equation gradually increases, and the peak area corresponding to the carboxyl functional group also gradually increases. And the rate and amount of water release gradually increase. For sodium polyacrylate, with the increase in the number of wet-dry- cycles, the increase in the content of calcium, magnesium, and aluminum elements is accompanied by a significant decrease in the content of sodium elements. In contrast, the calcium content on the surface of polyacrylic acid-acrylamide copolymer increased, but the sodium content only slightly decreased.

Enhancing mechanical performance of boronic ester based vitrimers via intermolecular boron–nitrogen coordination

Malleability and reprocessability of cross-linked polymers can be achieved via exchange reactions of the boronic ester crosslinking. Herein, we report a facile strategy to fabricate and modulate vitrimers by introducing intermolecular boron-nitrogen coordinated boronic ester crosslinking. Using a one-pot reaction, a series of boronic ester vitrimers based on polybutyl acrylate (PBA) was synthesized. The nitrogen containing monomer dimethylaminoethyl methacrylate (DMAEMA) was successfully copolymerized in the backbone to generate intermolecular boron-nitrogen (B–N) coordination. The presence of B–N coordination increases intermolecular interactions, leading to a denser crosslinked network structure and an elevated glass transition temperature. With the formation of B–N coordination, PBA-xB-yN samples at the same crosslinking density exhibit higher elongation at break and tensile strength. These samples dissipate more energy at the same strain and show a more pronounced strain rate dependency, highlighting the sacrificial role of the B–N coordination bonds. Stress relaxation experiments reveal that the intermolecular B–N coordination promotes faster relaxation of PBA-xB-yN compared to PBA-xB due to accelerated exchange dynamics of boronic ester. Mechanical reinforcement after recycling is observed in PBA-1B–2N, indicating that structural optimization of chemical and physical crosslinking occurs during thermal reprocessing. This study will provide a new strategy to fabricate boronic ester based vitrimeric materials with mechanical reinforcement and toughness enhancement.

Novel Composite Rejuvenators Development and Comparative Analyzes of Epoxy versus Diisocyanate Rejuvenators in Rejuvenating Aged SBS-Modified Asphalt Binders

Currently, many high-grade highways are undergoing expansion and remodeling phases. Utilizing recycled Styrene-Butadiene-Styrene (SBS) modified asphalt mixtures not only increases waste material utilization but also offers significant environmental benefits. In pursuit of high-quality rejuvenation of aged SBS-modified asphalt binders (SBSMA), this research leveraged aromatic oil (AO) as the component rejuvenator and introduced two novel SBS rejuvenators: ethylene glycol diglycidyl ether (GDE) and isophorone diisocyanate (IPDI). Furthermore, the study explores the mechanisms and effectiveness of both epoxy and diisocyanate rejuvenators, which are commonly used in SBS rejuvenation, specifically focusing on reconstructing cross-linked network structures within rejuvenated SBSMA. Findings indicate that during rejuvenation with diisocyanate rejuvenators and AO, the amide groups effectively react with carboxyl and ester groups in aged SBS, thus reconstructing the SBS modifiers. The rejuvenated SBS subsequently absorbs AO and light components, leading to swelling and the reconstruction of cross-linked network structures. Nevertheless, the rejuvenation efficacy of epoxy rejuvenators was relatively limited due to their low reactive nature or adverse side reactions that could degrade the rejuvenated SBS molecules, resulting in less effective reconstruction of the network structure. The specific differences in the reconstruction of network structures were reflected that diisocyanate rejuvenators improved the road performance of rejuvenated SBSMA under both high and low temperatures, reaching or even surpassing unaged SBSMA, while the performance of epoxy rejuvenators was closer to that achieved using AO alone. Overall, diisocyanate rejuvenators outperformed epoxy rejuvenators in repairing SBS, significantly enhancing the performance of SBSMA. This study provides valuable insights into achieving high-quality rejuvenation of SBSMA, which can significantly enhance the efficiency and quality of rejuvenation in high-grade roadways.

Constructing multiple bonding mechanisms with a novel lignin-activated modified polymer core for the fabrication of strong, water-resistant, and mildew-resistant adhesives

Biobased adhesives play a pivotal role in the development of eco-friendly wood products, and phytogenic protein as a biobased material preparation adhesive has the advantages of sustainable development and green environmental protection. Current researches focus and challenge lie in developing phytogenic protein adhesives that do not emit formaldehyde and possess high water-resistant bonding strength and anti-mold properties through the use of biobased cross-linkers instead of chemical cross-linkers. In this study, lignin, a natural polymer material, was used as raw material to fabricate a novel crosslinker, and a cross-linking network structure was constructed with lignin as the cross-linking core and multiple bonding effects of hydrogen and chemical bonds. In addition, lignin-based crosslinker was prepared to replace the chemical crosslinker while successfully activating lignin to improve the crosslinking degree between lignin and the protein matrix. This study addressed environmental pollution and cost issues associated with the extensive use of chemical cross-linkers in phytogenic protein adhesives. The water-resistant bonding strength of the prepared phytogenic protein adhesive reached 1.21 MPa, and the mechanical properties of the prepared phytogenic protein adhesive were increased by 188 % compared with the ordinary phytogenic protein adhesive and exhibited effective anti-mold properties. This research provided a novel approach for creating sustainable, environmentally friendly adhesives and held significant implications for producing industrial wood-based panels.

Synthesis and properties of temperature-responsive shape memory polyurethane with secondary crosslinked network structure based on LPO

Polyurethane has emerged as an excellent potential candidate for shape memory materials due to its microphase-separated structure with alternately connected hard and soft segments. In this study, SMPU of different molecular weights were prepared with poly(caprolactone) diol (PCL), hexamethylene diisocyanate (HDI), 1, 6-hexanediamine (HMDA), trimethylolpropane tris (3-mercaptopropionate) (TMPMP), and Dilauroyl peroxide (LPO). LPO as a chemical cross-linking agent can induce secondary cross-linking, which leads to the formation of a strong and stable secondary cross-linking network, and this network can be transformed into a supplier of internal stresses, so that the network exhibits excellent bidirectional shape memory effects. The effects of thermal and shape memory properties were investigated by TGA, DSC and DMA tests, the phase transition temperature of the SMPU was studied and the shape recovery process was recorded. The results show that the SMPU synthesized by PCL2k has good shape memory performance, with a reversible strain of up to 16.1 %, and the average shape fixation and recovery rates of 92.83 % and 99.98 %, respectively, with good shape memory performance, which is expected to show a wide range of application prospects and value of use in the fields of smart fabrics, biomedicine, sensing drive, aerospace and so on.

Melamine formaldehyde resin adhesive toughened with graphene oxide: Structures and properties

The melamine-formaldehyde (MF) resin adhesive was modified by graphene oxide (GO), the chemical structure, wettability, bonding performance, tensile properties, curing performance and thermal properties of the modified resin were analyzed, and the toughening mechanism was also discussed in this study. The results showed that: (1) The MF resin with a high molar ratio possessed stable methylene ether bonds, which could easily generate parallel folding in space to form a π-π stacking supramolecular self-assembly special structure, with the potential of enhancing the toughness of molecular structures. (2) GO contained a large number of oxygen-containing reactive functional groups, which could further lower the curing temperature of the MF resin. A dense cross-linked network structure improved the thermal stability of the resin. (3) The bonding strength and toughness of the resin were significantly improved when the content of GO was 0.1 wt%. However, due to the large specific surface area and the intense π-π interaction between sheets, GO was easy to agglomerate, and the properties of the resin with GO content of 0.4 wt% degraded sharply. (4) The crystallinity of the MF resin modified by GO decreased, and the surface energy and plastic deformation energy increased due to the increased fracture crack path and fracture surface of the resin, which was the macro-reason for the improvement of toughness. (5) The strong π-π interaction between GO sheets and π-π accumulation between triazine rings were like parallel “springs” in the molecular structure of the resin, which might be the internal reason for the improvement of toughness. In addition, it was also proved that this special structure could limit the activity of hydroxymethyl and the release of free formaldehyde in the resin.

Integrated wood surface densification and Al2O3/melamine impregnated paper coating process: Properties evaluation

Fast-growing wood is limited in its use due to its low density and poor strength. Strengthening its texture and enhancing its performance is crucial for maximizing the economic value of fast-growing wood. This study employed a one-step process of unilateral surface densification and coating, which involved compressing the surface of poplar wood and simultaneously applying Al2O3/melamine impregnated paper to achieve paint-free reinforcement modification. After modification, a cross-linking network structure was established at the interface of poplar wood and Al2O3/melamine impregnated paper with bonding strength satisfied superior product requirements for solid wood flooring as per GB/T 15036.1–2018. The natural texture and original aesthetic characteristics of poplar wood were preserved, the surface scratch resistance hardness was as high as 9 H, and the color and luster of the surface showed no obvious changes after being polluted by coffee and 25 % NaOH solution. Additionally, the functionalized wood also exhibited excellent mechanical properties with a modulus of rupture (MOR) of 112.6 MPa and a modulus of elasticity (MOE) reaching 9.33 GPa; the indentation diameter was only 7.5 mm, indicating excellent impact resistance, surpassing that of hardwood commonly used for wood flooring.

Control over phase structures’ evolution within the novel organic–inorganic hybrid system for achieving a comprehensive thermal, mechanical, and dielectric properties

Significant challenges persist in developing high-performance, wave-transparent capable of operating above 500 ℃ using organic–inorganic hybrid materials. This study introduced a novel, highly reactive terminal carborane monomer, 4-(3-carborylphenyl) phthalonitrile (CB-Ph), to create a cross-linked network structure and inorganic phase. By integrating this with the conventional high-performance poly (phthalazine ether nitrate ketone) (PPENK), a novel organic–inorganic hybrid system was successfully constructed. Simultaneously, the modifications in the inorganic layer and phase structure of the material with increasing CB-Ph content were examined through nanoindentation and SEM analysis systems, establishing a structural foundation for optimizing the balance between thermal resistance, mechanical strength, and dielectric properties (balance of T-M−D). The thermal performance testing results indicates that the hybrid materials achieved high glass transition temperatures (Tg exceeding 500 ℃). This enhancement is attributable to the synergistic effects of cyanide side group micro-crosslinking and the phthalonitrile crosslinking network, which collectively restricted the movement of chain segments. The P-CB50 resin (PPENK+50 wt% CB-Ph), with its distinctive transition phase structure, boasts the most outstanding comprehensive performance. In terms of thermal stability, it not only features a Tg surpassing 500 ℃ In terms of thermal stability, it not only has a Tg exceeding 500 °C, but also loses only 5 % weight at 599.3° C in a nitrogen atmosphere (Td5%–N2 = 599.3 °C). Mechanical testing reveals that the flexural strength of the P-CB50 composite reaches an impressive 384.3 MPa, while the impact strength attains a significant 109.4 KJ/m2. Even at temperatures as high as 500 ℃, the dielectric constant of the P-CB50 composite material remains below 4, underscoring its superior high temperature wave-transparent properties. These results have firmly established a correlation between the phase structure of the hybrid system and the comprehensive performance of T-M−D, thereby laying a solid foundation for the development of high-temperature resistant and wave-transparent materials with enhanced overall performance.

Jellyfish‐Inspired Polyurea Ionogel with Mechanical Robustness, Self‐Healing, and Fluorescence Enabled by Hyperbranched Cluster Aggregates

AbstractIonogels are promising for soft iontronics, with their network structure playing a pivotal role in determining their performance and potential applications. However, simultaneously achieving mechanical toughness, low hysteresis, self‐healing, and fluorescence using existing network structures is challenging. Drawing inspiration from jellyfish, we propose a novel hierarchical crosslinking network structure design for in situ formation of hyperbranched cluster aggregates (HCA) to fabricate polyurea ionogels to overcome these challenges. Leveraging the disparate reactivity of isocyanate groups, we induce the in situ formation of HCA through competing reactions, enhancing toughness and imparting the clustering‐triggered emission of ionogel. This synergy between supramolecular interactions in the network and plasticizing effect in ionic liquid leads to reduced hysteresis of the ionogel. Furthermore, the incorporation of NCO‐terminated prepolymer with dynamic oxime–urethane bonds (NPU) enables self‐healing and enhances stretchability. Our investigations highlight the significant influence of HCA on ionogel performance, showcasing mechanical robustness including high strength (3.5 MPa), exceptional toughness (5.5 MJ m−3), resistance to puncture, and low hysteresis, self‐healing, as well as fluorescence, surpassing conventional dynamic crosslinking approaches. This network design strategy is versatile and can meet the various demands of flexible electronics applications.

Research of influence of diluent on the mechanical behavior of triaxial warp-knitted composites

The composites are prepared by different processes of reinforcement and matrix, which are affected by the properties of reinforcement and matrix. In this study, composite specimens were fabricated using vacuum-assisted resin infusion (VARI) with varying mass fractions (0%, 5%, 10%, and 15%) of a diluent mixed with the resin and curing agent, serving as the matrix. Triaxial warp-knitted glass fabric was employed as the reinforcement material. The impact of the diluent mass fraction on the bending, impact, and creep properties of the composites was investigated. The least squares fitting method was applied to analyze the experimental data, leading to the establishment of a mathematical model correlating the diluent mass fraction with the bending strength. The optimal diluent mass fraction for achieving the best bending properties was determined. Furthermore, the failure mechanisms of the composites were examined through an analysis of their thermodynamic properties, reaction principles, and fracture morphologies. The results show that the epoxy group in the diluent will be connected to the cross-linking network structure of epoxy resin by ring-opening reaction, and excessive addition will lead to the increase of flexible chain segments, which makes the mechanical properties of the specimens increase first and then decrease. The mathematical model was verified by experiments, and the mass fraction of diluent was 9.65% when the bending property was optimal.

Modulation of Mechanical Properties of Silica-Filled Silicone Rubber by Cross-Linked Network Structure.

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory-Rehner model and Mooney-Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber.

Preparation and characterization of UV-curable coatings based on waterborne polyurethane acrylate/g-C3N4 co-crosslinked network for wood materials

Wood materials are often damaged due to exposure to environmental factors including humidity changes, temperature fluctuations, and ultraviolet radiation, resulting in surface aging, deformation, and cracking. Therefore, developing a new wood coating with good mechanical properties and weather resistance is conducive to improving the usability and service life of wood as an outdoor material. In this study, graphitic carbon nitride (g-C3N4) with a characteristic crystal structure was synthesized using melamine as raw material. By constructing a g-C3N4 /polyurethane acrylate co-crosslinked network, a UV-curable wood coating with excellent interfacial adhesion was prepared, which retained the natural aesthetic texture of the wood and imparted good wear resistance, anti-wetting property, and aging resistance to the wood material. Subsequently, the formation process and cross-linking reaction mechanism of the coating were revealed by XRD, FTIR and XPS measurements. Compared with untreated samples, coatings with a cross-linked network structure exhibited enhanced resistance to external environmental changes. As the content of the g-C3N4 increased (>1.0 %), the mechanical properties were significantly improved, with the mass loss rate and damaged area decreasing by 56.9 % and 60.0 %. Meanwhile, with the increased cross-link density of the coating, the water and heat resistance of the wood increased by 22.77 % and 260 %, respectively. After a seven-day UV aging resistance test, the ΔE values only changed by 10.28 %, showing good weathering resistance. This design and synthesis of wood coating provides an effective technology for the long-term use of outdoor wood material.

Tracking protein aggregation behavior and molecular interactions induced by conformational alterations in the formation of myofibrillar protein-Abelmoschus manihot gum mixed gels during heating process

The present study aimed to systematically investigate the effects of different Abelmoschus manihot gum (AMG) concentrations (0–0.5%, w/w) on the formation of myofibrillar protein (MP) gels during heating process (30–80 °C) based on conformational alterations, protein aggregation behavior and molecular interactions. With the increase of temperature, the fluorescence intensity and α-helix content significantly decreased, revealing conformational transition of MP molecular. Dynamic rheological results indicated that MP had completely denatured and formed temporary gel at 50 °C, and completely formed irreversible cross-linked three-dimensional network structure at 80 °C. Moreover, the addition of AMG decreased the fluorescence intensity, as well as induced the transition of MP from α-helix to β-sheet during the whole heating process. Furthermore, AMG addition significantly decreased the turbidity and improved solubility of MP (P < 0.05), especially for at 0.3% AMG concentration, indicating that AMG accelerated the early unfolding and aggregation of MP during heating process. This was verified by the dynamic rheological results. Additionally, hydrophobic interactions and disulfide bonds were the main molecular forces to induce the formation of MP-AMG mixed gel. Therefore, our present results provided the new insights into the formation of MP-AMG mixed thermal-induced gel, and also contributed to the practical application of AMG in meat processing.

Liquid-free, tough and transparent ionic conductive elastomers based on nanocellulose for multi-functional sensors and triboelectric nanogenerators

Stretchable and transparent ionic conductors have attracted great interest due to their promising applications in flexible wearable electronics. The obvious drawbacks of gel-based ionic conductors such as hydrogels (e.g., evaporation or freezing of water) have driven the demand for liquid-free ionic conductors. This paper reports a new strategy for fabricating transparent, liquid-free ionic conductive elastomers based on renewable nanocellulose. A three-dimensional cellulose skeleton was constructed through ionic cross-linking, and the physically and chemically cross-linked dual network structure was prepared by in situ polymerization of the polymerizable deep eutectic solvent (PDES) therein. The homogeneous three-dimensional cross-linked network provides a site for energy dissipation and ionic migration. Results show that the elastomers retain good transparency and achieve significantly improved mechanical strength, toughness and ionic conductivity. Therefore, they can be applied as multi-functional sensors and triboelectric nanogenerators (TENG). For the optimized TENG, output voltage, current and charge reach 115 V, 6 μA, and 40 nC, respectively. A maximum output power density of 0.35 W/m2 is achieved, and the collected mechanical energy can light up LEDs and power an electronic clock. In addition, the elastomers maintain reliable performance even at low/high temperatures, enabling use in harsh environments. In conclusion, this study developed a promising strategy for the construction of sustainable liquid-free ionic conductors utilizing natural polysaccharides.

A Novel Gelatin Binder with Helical Crosslinked Network for High-Performance Si Anodes in Lithium-Ion Batteries.

Silicon(Si) is a promising anode material for lithium-ion batteries, but its large volume expansion during cycling poses a challenge for the binder design. In this study, a novel gelatin binder is designed and prepared with a helical crosslinked network structure. This gelatin binder is prepared by enzymatic crosslinking and immersion in Hofmeister salt solution, which induces the formation of network and helical secondary structures. The helical crosslinked network structure can be analogous to a spring group system to effectively dissipate the stress and strain caused by the Si expansion. The gelatin binder is further partially carbonized by low-temperature pyrolysis, which improves its conductivity and stability. The Sianode with the optimized gelatin binder exhibits high initial coulombic efficiency, excellent rate performance, and long-term cycling stability. This study provides an innovative approach for the preparation of high-performance Si anodes, namely by controlling the molecular configuration of the binder to significantly improve the cycle stability, which can also be applied to other high-capacity anode materials that suffer from large volume changes during cycling.

Nitrogen configuration modulation of porous graphitic carbon nanosheets for superior capacitive energy storage

Carbon nanosheets with layer-stacked porous structures and surface functionalized groups are beneficial for efficient ion storage in supercapacitor electrode materials, but achieving high cost-effectiveness and controllable surface groups remains a significant challenge. Herein, the biomass-derived chitosan and sodium alginate are selected as raw materials for self-assembly reaction with phytic acid as a cross-linking agent. The protonated chitosan and sodium alginate form a cross-linked network structure through hydrogen bonding and electrostatic adsorption, which is subsequently carbonized and activated to synthesize porous graphitic carbon nanosheets (PNPCN-X). PNPCN-X realizes an efficient distribution of porous and graphitic structures. It's noteworthy that phytic acid facilitates the fixation of N atoms, and various N configurations can be adjusted by altering the content of phytic acid. Optimized PNPCN-1.5 exhibits a high content of structurally stable pyridinic-N and graphitic-N configurations, which are confirmed to serve as active sites substantially augmenting the ion adsorption capacity through Density Functional Theory (DFT) calculations. Benefiting from its exceptional physicochemical properties, PNPCN-1.5 achieves 322 F g−1 as electrode materials in the three-electrode system, while the symmetrical supercapacitor assembled with EMIMBF4 electrolyte attains 56.29 W h kg−1. Furthermore, various kinetic analyses extensively elucidate its capacitance distribution characteristics and ion diffusion rates.

Performance enhancement of silica filled natural rubber nanocomposites using organic deep eutectic solvent

Silica is an important filler of “green tires” while its dispersion in the aid of silane coupling agents emits volatile organic compounds during rubber compounding and its invariably agglomeration in nonpolar rubber matrices enhances strain softening. Herein a highly active deep eutectic solvent (DES), synthesized using stearic acid as hydrogen bond donor and tetrabutylammonium chloride as hydrogen bond acceptor, is used to tailor reinforcement and softening behaviors and to replace the silane coupling agents for preparing volatile organic compounds-free nanocomposites. The results show that DES can regulate the crosslinking network structure of rubber matrix and accelerate the vulcanization by reacting with non-rubber components in natural rubber (NR) and by improving the proportion of disulfidic linkage. Furthermore, DES is able to improve the dispersion of silica, crosslinking density of NR and the interfacial interaction between silica and NR, and slow down the thermo-oxidative aging behavior. It could also weaken the damping and softening accompanying Mullins effect for the nanocomposites vulcanizates at high strains. In comparison with silane, DES endows the nanocomposites with superior vulcanization and mechanical properties, providing guides to mediate the reinforcement and strain softening behaviors and manufacture high-performance “green tires” in an energy-efficient approach.

Jellyfish-Inspired Polyurea Ionogel with Mechanical Robustness, Self-Healing, and Fluorescence Enabled by Hyperbranched Cluster Aggregates.

Ionogels are promising for soft iontronics, with their network structure playing a pivotal role in determining their performance and potential applications. However, simultaneously achieving mechanical toughness, low hysteresis, self-healing, and fluorescence using existing network structures is challenging. Drawing inspiration from jellyfish, we propose a novel hierarchical crosslinking network structure design for in situ formation of hyperbranched cluster aggregates (HCA) to fabricate polyurea ionogels to overcome these challenges. Leveraging the disparate reactivity of isocyanate groups, we induce the in situ formation of HCA through competing reactions, enhancing toughness and imparting the clustering-triggered emission of ionogel. This synergy between supramolecular interactions in the network and plasticizing effect in ionic liquid leads to reduced hysteresis of the ionogel. Furthermore, the incorporation of NCO-terminated prepolymer with dynamic oxime-urethane bonds (NPU) enables self-healing and enhances stretchability. Our investigations highlight the significant influence of HCA on ionogel performance, showcasing mechanical robustness including high strength (3.5 MPa), exceptional toughness (5.5 MJ m-3), resistance to puncture, and low hysteresis, self-healing, as well as fluorescence, surpassing conventional dynamic crosslinking approaches. This network design strategy is versatile and can meet the various demands of flexible electronics applications.

High value-added use of waste photosensitive polyimide to develop low-shrinkage UV-curable inks for digital light projection technology

In the mass industrial production process of polyimide photoresists, waste generation is inevitable due to unqualified molecular weights, inappropriate ionic content of resins, or storage expiration. Consequently, the recycling and reuse of waste photosensitive polyimide (w-PSPI) is a growing concern in both scientific and industrial communities. In this work, w-PSPI was explored to prepare photocurable, fully crosslinked inks for digital light projection technology (DLP). For this purpose, suitable photoactive solvents and crosslinking agents were first screened to overcome the issue of large shrinkage caused by solvent volatilization. The formation of cross-linked network structures during DLP processing and subsequent imidization was also investigated. As a result, a polyimide DLP ink with minimum size shrinkage (less than 5 %) was proposed. For a given active solvent, the mechanical behavior and heat resistance of DLP-formed objects were significantly influenced by the ratio of short-chain and long-chain crosslinkers and the imidization temperature. By optimizing ink composition and imidization temperature, the DLP-formed objects showed high heat resistance (Td5 > 385 °C, Tg > 150 °C) and balanced mechanical properties of strength and toughness (Modulus ≥1 GPa, elongation at break >5 %). This w-PSPI ink has been successfully utilized to manufacture several complex 3D structures and vertical 3D microarrays with 100-µm on a limited-resolution DLP printer. This study not only points the direction for the high-added utilization of w-PSPI but also demonstrates the potential for expanding PSPI application from 2D lithography to 3D micro-manufacturing.