Dual Crosslinking Research Articles

Bioinspired anion exchange membranes with dual steric cross-linking centers for industrial-scale water electrolysis

A precise molecular regulation approach was proposed to design high-performance and high-stability spatially crosslinking AEMs that boosted the industrial-scale AEM-WE.

Endowing rubber with intrinsic self-healing properties using thiourea-based polymer.

Self-healing polymers are extensively researched for the sustainability of materials. The introduction of dynamic networks instead of traditional cross-linkers for an autonomous healing mechanism in elastomers is a promising strategy for improving rubber properties. However, exchangeable covalent bonds in a dynamic network generally rely on external stimulants and fillers, which can compromise the material's performance. Herein, we introduce a mechanically strong yet resilient and independent self-healing polymeric network by dual cross-linking of bonds based on covalent and non-covalent dual interaction. The thiourea-based polymer polyether thiourea ethylene glycol (PTUEG) was blended with natural rubber (NR) and epoxidized natural rubber (ENR) to strengthen the mechanical characteristics of the material NR-ENR-PTUEG3. In the material, the thermoplastic polymer PTUEG3 applied the thiourea linkage as a hydrogen bonding and dynamic covalent motif together to enhance mechanical adaptability in a self-healing polymer network exhibiting stiffness, toughness, and resilience, thereby extending its longevity. The resulting mechanical characteristics of the NR-ENR-PTUEG3 with 25 phr PTUEG3 exhibited tensile stress 4.8 ± 0.3 MPa and high elongation at break 833 ± 0.1%, demonstrating far better performance than that of pristine NR, and 85% recovery of its original strength at ambient temperature. The healing behaviour is strongly influenced by thiourea-based polymer contents, enabling autonomous self-healing at ambient temperature, exhibiting in situ load-bearing efficiency in the repaired material, and maintaining their mechanical characteristics.

Engineering chitosan into a recyclable and flame-resistant gel electrolyte via a dual cross-linking strategy for flexible supercapacitors

A dual cross-linking strategy was developed using LA and sodium borate to engineer chitosan into flame-resistant and recyclable GPEs with satisfactory mechanical properties and high ionic conductivity for application in flexible SCs.

Reversible dual crosslinking in anthracenyl functionalized butyl elastomers based on ionic interaction and (4 + 4) cycloaddition mechanisms

Dual-healable fluorescent butyl rubber based on ionic interaction and dynamic (4 + 4) cycloaddition mechanisms.

Strong and Tough Biofibers Designed by Dual Crosslinking for Sutures

AbstractHigh‐performance bio‐based fibers have unique advantages in biocompatibility for biomedical applications, such as sutures, hernia patches, and blood vessels. Herein, strong and tough biofibers based on regenerated silk fibroins (RSFs) are designed by a dual‐crosslinking strategy and prepared continuously in situ via a single‐channel microfluidic device. During the wet spinning process, covalent bonds between tyrosines are introduced by photo crosslinking and coordination interactions of Zn2+ ions with serines are built between RSFs, forming a dual‐crosslinked, and inter‐connected network and effectively improving the mechanical performances of RSF fibers. By optimizing the wet spinning parameters and applying an optimal post‐stretching treatment, dual‐crosslinked RSF fibers exhibit an excellent tensile strength of 891 MPa, a remarkable Young's modulus of 15.0 GPa, a large tensile strain of 20.1%, and an outstanding toughness of 114 MJ m−3, which are superior to other regenerated biofibers. In addition to the outstanding mechanical performances, dual‐crosslinked RSF fibers also possess excellent temperature adaptability, fatigue resistance, biocompatibility, and biodegradability, making them ideal candidates for biomedical applications. In vivo tests of dual‐crosslinked RSF fibers as sutures demonstrate a good wound healing performance with smaller scar and lower inflammation.

Tuning Physical Properties of GelMA Hydrogels through Microarchitecture for Engineering Osteoid Tissue.

Gelatin methacryloyl (GelMA) hydrogels have gained significant attention due to their biocompatibility and tunable properties. Here, a new approach to engineer GelMA-based matrices to mimic the osteoid matrix is provided. Two cross-linking methods were employed to mimic the tissue stiffness: standard cross-linking (SC) based on visible light exposure (VL) and dual cross-linking (DC) involving physical gelation, followed by VL. It was demonstrated that by reducing the GelMA concentration from 10% (G10) to 5% (G5), the dual-cross-linked G5 achieved a compressive modulus of ∼17 kPa and showed the ability to support bone formation, as evidenced by alkaline phosphatase detection over 3 weeks of incubation in osteogenic medium. Moreover, incorporating poly(ethylene) oxide (PEO) into the G5 and G10 samples was found to hinder the fabrication of highly porous hydrogels, leading to compromised cell survival and reduced osteogenic differentiation, as a consequence of incomplete PEO removal.

Thermoresponsive Alginate-Graft-pNIPAM/Methyl Cellulose 3D-Printed Scaffolds Promote Osteogenesis In Vitro.

In this work, a sodium alginate-based copolymer grafted by thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) chains was used as gelator (Alg-g-PNIPAM) in combination with methylcellulose (MC). It was found that the mechanical properties of the resulting gel could be enhanced by the addition of MC and calcium ions (Ca2+). The proposed network is formed via a dual crosslinking mechanism including ionic interactions among Ca2+ and carboxyl groups and secondary hydrophobic associations of PNIPAM chains. MC was found to further reinforce the dynamic moduli of the resulting gels (i.e., a storage modulus of ca. 1500 Pa at physiological body and post-printing temperature), rendering them suitable for 3D printing in biomedical applications. The polymer networks were stable and retained their printed fidelity with minimum erosion as low as 6% for up to seven days. Furthermore, adhered pre-osteoblastic cells on Alg-g-PNIPAM/MC printed scaffolds presented 80% viability compared to tissue culture polystyrene control, and more importantly, they promoted the osteogenic potential, as indicated by the increased alkaline phosphatase activity, calcium, and collagen production relative to the Alg-g-PNIPAM control scaffolds. Specifically, ALP activity and collagen secreted by cells were significantly enhanced in Alg-g-PNIPAM/MC scaffolds compared to the Alg-g-PNIPAM counterparts, demonstrating their potential in bone tissue engineering.

A double‐dynamic‐bond crosslinked multifunctional conductive hydrogel with self‐adhesive, remoldability, and rapid self‐healing properties for wearable sensing

AbstractIn recent years, conductive hydrogels have been designed as flexible sensors with broad application prospects in the field of smart wearable devices. However, the coordination of the mechanical properties, self‐healing capability, and conductivity of hydrogels has always been a challenge. In this work, a multifunctional conductive hydrogel with self‐adhesive, re‐shapeable, and rapid self‐healing abilities (PB‐PACS‐PM3 (self‐healing efficiency) = 98.8% in 15 s) was prepared by incorporating protocatechualdehyde modified carboxymethyl chitosan (PA@o‐CMCS) and PDA‐modified MXene (PDA@MXene) into the interchain of polyvinyl alcohol through dynamic borate ester crosslinking. The dynamic Schiff base reaction not only effectively introduced o‐CMCS as a mechanical enhancer but also improved the viscoelasticity and self‐healing capability of the hydrogel through the dual dynamic bond crosslinking structure. The PDA@MXene nanosheets are uniformly distributed in the hydrogel, providing the composite system with excellent conductivity (the conductivity of PB‐PACS‐PM3 hydrogel is 1.5 S/m) and strain sensitivity (the response time and recovery time of the hydrogel sensor are 230 and 260 ms, respectively), while the tensile strength of the hydrogel is improved to 0.035 MPa. Due to all these advantages, this conductive hydrogel can be assembled into flexible wearable sensors for rapid and accurate monitoring of various physiological activities of the human body, such as finger, wrist, elbow, and knee bending vibrations, among others.

A sodium alginate/carboxymethyl chitosan dual-crosslinked injectable hydrogel scaffold with tunable softness/hardness for bone regeneration

Recently, injectable dual-crosslinked (DC) hydrogel scaffolds have attracted many attentions as a class of excellent bone regeneration biomaterials with in-situ tunable functions. However, the design of injectable DC hydrogels with cell behavior-compatible network structure and mechanical property remains a bottleneck. Herein, based on the in-situ gelling method, we constructed an injectable CMCS/PEG+SA/CaCl2 (CPSC) chemical/physical DC hydrogel scaffold with tunable softness/hardness mechanical properties and good biocompatibility. The formation mechanism and properties of the CPSC hydrogel scaffold were investigated by FTIR, XRD, rheometry, and mechanical testing. It is found that proper softness/hardness mechanical properties can be obtained by adjusting the secondary network structure of the hydrogel. The CPSC hydrogel scaffold prepared under optimal conditions can effectively promote cell infiltration, nutrient transport, and the osteogenic differentiation of rat bone mesenchymal stem cells (rBMSCs). The in vivo experiments show that the rBMSCs-loaded injectable CPSC hydrogels with appropriate mechanical properties can effectively promote bone reconstruction. This study has provided important guidance for the construction of injectable DC hydrogels with adjustable softness/hardness to promote osteogenesis for bone defect repair.

Mixed ion-electron conductive binders coupling superior stiffness and toughness establish dual crosslinking stable silicon anodes

The unstable solid electrolyte interface, huge volume expansion, and poor electrical conductivity severely hamper the commercial application of silicon (Si) anode with high capacity for next-generation lithium-ion batteries. Herein, a mixed ion–electron conductive (MIEC) binder coupling stiffness and toughness is designed to fabricate strong chemical bonds and physical hydrogen bonds with hydroxylated carbon nanotubes (CNT-OH) and Si particles by esterification reaction between sulfonic acid and hydroxyl groups. The dual crosslinking efficiently alleviates large stress from Si and maintains the electrodes’ structural integrity. The excellent synergistic effect of ion and electron conductivity of the prepared binder enhances the kinetics of lithium-ion and electron transport of the Si electrodes, achieving commercial areal capacity and a long lifespan. Thus, the Si anode with the prepared resultant binder delivers a high reversible capacity of 3079 mAh/g at 0.6 A/g after 200 cycles and retains a remarkable capacity of 2151 mAh/g at a high current density of 2 A/g even after 500 cycles. The work demonstrates the great potential of this binder design strategy to achieve the overall property promotion and practical feasibility of Si and other electrodes suffering from their low conductivity and dramatic volume changes.

Unlocking the Power of Multicatalytic Synergistic Transformation: toward Environmentally Adaptable Organohydrogel.

A sustainable and efficient multicatalytic chemical transformation approach is devised for the development of all-biobased environmentally adaptable polymers and gels with multifunctional properties. The catalytic system, utilizing Lignin aluminum nanoparticles (AlNPs)-aluminum ions (Al3+ ), synergistically combines multiple catalytic cycles to create robust, mechanically stable, and versatile organohydrogels. Single catalytic cycles alone fail to achieve desired results, highlighting the importance of cooperatively combining different cycles for successful outcomes. The transformation involves free radical crosslinking, reversible quinone-catechol reactions, and an autocatalytic mechanism, resulting in a dual crosslinking strategy that incorporates both covalent and ionic crosslinking. This approach creates a dynamic gel system with combined energy dissipation and storage mechanisms. The engineered organohydrogels demonstrate vital multifunctionalities such as good thermal stability, self-healing, and adhesive properties, flame-retardancy, mechanical resilience and durability, conductivity, viscoelastic properties, environmental adaptability, and resistance to extreme conditions such as freezing and drying. The developed catalytic technology and resulting gels hold significant potential for applications in flexible electronics, energy storage, actuators, and sensors.

Production of green-natural and “authentic” cultured meat based on proanthocyanidins-dialdehyde chitosan-collagen ternary hybrid edible scaffolds

Cultured meat has the potential to fulfill the meat demand for the growing human population, but cultured meat development will be required to simplify the production process and produce naturally cultured meat, such as no longer stripping off scaffolders and adding artificial dyes. In this study, proanthocyanidins (PC) and dialdehyde chitosan (DAC) were employed as dual crosslinkers with collagen to prepare a hybrid 3D edible scaffold for the production of high-quality cell-cultured meat. The results revealed that the scaffold was biocompatible and could offer robust mechanical support and adhesion sites for bovine myoblasts, enabling long-term cell culture. Meanwhile, the Col-PC-DAC scaffold promoted the myogenic differentiation of bovine myoblasts and extracellular matrix protein secretion, further affecting the texture of cultured meat. After cooking the cultured meat and beef, it was shown that the cultured meat had some similarities to beef in color and flavor. Importantly, our findings demonstrate that cultured meat can acquire a color remarkably similar to that of conventional beef without the need for artificial dyeing. This breakthrough not only simplifies the production process but also ensures a more natural and appealing appearance of cultured meat. In conclusion, the proanthocyanidins-dialdehyde chitosan-collagen hybrid 3D edible scaffolds provide a new option for producing cultured meat that satisfies consumer expectations.

Preparation of fluorinated poly(aryl ether) with high dimensional stability and high temperature resistance by photo‐thermal dual crosslinking reaction

AbstractImproving the dimensional stability is significant for fluorinated poly(aryl ether) (FPAE). In this work, zirconium tungstate (ZrW2O8) with negative thermal expansion (NTE) modified by thiol groups is successfully obtained by surface modification with 3‐(trimethoxysilyl)‐1‐propanethiol. Then, the dispersion of ZrW2O8 is improved and a certain crosslinked structure is formed by click reaction between thiols on the surface of ZrW2O8 and allyl groups on the backbone of FPAE. On this basis, the residual allyl groups on the FPAE can undergo addition reaction under heating conditions to further form crosslinked structure. Due to the introduction of photo‐thermal dual crosslinked structure, the dimensional stability of FPAE is significantly improved, and the coefficient of thermal expansion decreased by 64.3% compared to the unoptimized samples. Meanwhile, the dielectric properties are characterized with dielectric constant and dissipation factor of 3.70 and 0.008 at 1 kHz. Finally, the prepared film is used to assemble triboelectric nanogenerators, where the short‐circuit current, open‐circuit voltage and transferred charge is 3 μA, 30 V, and 10 nC, respectively. Crosslinked FPAE with high dimensional stability and high temperature resistance are successfully gained by avoiding the complexity of monomer synthesis and realizing higher performance with the same inorganic filler loading.Highlights Dual crosslinked structure is built by photo‐thermal dual crosslinking reaction. ZrW2O8 gains homogeneous dispersion in polymer matrix by photo‐crosslinking reaction. Introducing ZrW2O8 and dual crosslinked structure raises dimensional stability of film.

Multifunctional films with superior mechanical performance, transparency, antibacterial properties enabled by a physical and chemical dual crosslinking network construction

Exploring sustainable and bio-degradable alternative materials based on lignin and cellulose is expected to address the serious environmental problems caused by the continuous accumulation of petroleum plastic waste. One open question is how to make a high mechanical strength lignin-cellulose material without optical haze. Herein, a multifunctional lignin-cellulose film with excellent mechanical properties and high transparency is successfully prepared based on Schiff base chemistry along with multiple hydrogen bonding interactions. Combined with the chemical and physical double cross-linking network, positively charged aminated lignin improves the compatibility with dialdehyde cellulose and also optimizes the internal structure of the material. Significantly, the obtained films (ALDC10) deliver exceptional mechanical properties (tensile strength, 164.8 MPa and Young's modulus, 12.1 GPa), which are higher than those of some commercial petroleum-based plastics. The films endow superior transparency, antimicrobial (>50 %), UV shielding, and water vapor barrier properties, making them suitable for plastics replacement in active food (apple) packaging. Additionally, the transparent films show photothermal conversion properties, which have high potential applications in food vending machine to delay spoilage of foods with reduced energy consumption. This work establishes advanced valorization of cellulose and lignin, with superior performance, which is expected to replace petroleum plastics in various applications.

Mechanically robust hydrogel from thermosetting polybenzoxazine with dual crosslinking network

The main chain of polymer composition in hydrogels is mostly aliphatic and the crosslinking density is usually low, which renders the hydrogels with low mechanical strength. In this work, a kind of thermosetting resin, benzoxazine is used as the starting material to prepare the corresponding hydrogels by one-pot synthesis. The organic gels are firstly formed in dimethylformamide with the aid of catalyst, followed by extraction of water to give the hydrogels. It is revealed that due to the presence of covalent crosslinking and abundant hydrogen bonding, the as-prepared rigid hydrogels show extremely high compressive strength. The hydrogel with 55.8 wt% of water shows yield strength about 20 MPa and sustains compressive strength of 75 MPa (compressive stress of 30 kN, compressive strain of 67 %) without cracking. The hydrogel also show extremely high dielectric constant of 392,000, dielectric loss of 971,000, and ionic conductivity of 1.7 × 10−3 S/m at 100 Hz. Moreover, the responsiveness to pH variation suggests its potential application as smart responsive materials. To show the superiority of preparing functional composite hydrogels using this strategy, electroconductive and magnetic fillers are introduced and the as-prepared composite hydrogels show good electromagnetic shielding performance.

Sludge-derived hierarchically porous carbon electrode prepared via CaCO3-assisted dual crosslinking for enhanced phosphate electrosorption

Electrosorption is considered a promising technology to remove charged pollutants in an efficient and green way, wherein the electrode materials are crucial for achieving its high performance. In this study, a Zr-containing hierarchically porous carbon electrode (ZHPC-1-Ca) tailored for phosphate removal was synthesized based on alginate-like exopolysaccharides (ALE), a biomass extract of excess sludge. The gel-forming ability of ALE provided a basis for obtaining a conductive carbon matrix with well-dispersed metal active sites, and the pore structure of ALE-derived electrodes was simply regulated via a dual-crosslinking strategy. In the synthesis, CaCO3 acted as both the hard template and the crosslinker, while Zr facilitated pore formation during the secondary crosslinking process. ZHPC-1-Ca exhibited a maximum electrosorption capacity of 12.40 mg g−1 at 1.2 V, with a low energy consumption of 3.166 kWh kg−1-P. The electrosorption behavior was well fitted with the pseudo-first-order kinetics and the Langmuir isotherm model. Moreover, ZHPC-1-Ca maintained stable electrosorption performance under pH 4–10 and during twenty capture-release cycles (85.2%). The electrosorption mechanisms were primarily elucidated as electrostatic attraction, ligand exchange, and Lewis acid-base interaction, contributing to the enhanced and selective phosphate removal. This study achieves a simple and controllable synthesis of hierarchically porous carbon electrodes using sludge biopolymers, which extends the application of sludge-derived carbon in phosphate electrosorption.

Dual-crosslinked methacrylamide chitosan/poly(ε-caprolactone) nanofibers sequential releasing of tannic acid and curcumin drugs for accelerating wound healing

The objective of this research study is to develop novel composite nanofibers based on methacrylamide chitosan (ChMA)/poly(ε-caprolactone) (PCL) materials by the dual crosslinking and coaxial-electrospinning strategies. The prepared ChMA/PCL composite nanofibers can sequentially deliver tannic acid and curcumin drugs to synergistically inhibit bacterial reproduction and accelerate wound healing. The rapid delivery of tannic acid is expected to inhibit pathogenic microorganisms and accelerate epithelialization in the early stage, while the slow and sustained release of curcumin is with the aim of relieving chronic inflammatory response and inducing dermal tissue maturation in the late stage. Meanwhile, dual-drugs sequentially released from the membrane exhibited a DPPH free radical scavenging rate of ca. 95 % and an antibacterial rate of above 85 %. Moreover, the membrane possessed great biocompatibility in vitro and significantly inhibited the release of pro-inflammatory factors (IL-1β and TNF-α) in vivo. Animal experiments showed that the composite membrane by means of the synergistic effect of polyphenol drugs and ChMA nanofibers, could significantly alleviate macrophage infiltration and accelerate the healing process of wounds. From the above, the as-prepared ChMA-based membrane with a stage-wise release pattern of drugs could be a promising bioengineered construct for wound healing application.

A double-crosslinked nanocellulose-reinforced dexamethasone-loaded collagen hydrogel for corneal application and sustained anti-inflammatory activity

In cases of blinding disease or trauma, hydrogels have been proposed as scaffolds for corneal regeneration and vehicles for ocular drug delivery. Restoration of corneal transparency, augmenting a thin cornea and postoperative drug delivery are particularly challenging in resource-limited regions where drug availability and patient compliance may be suboptimal. Here, we report a bioengineered hydrogel based on porcine skin collagen as an alternative to human donor corneal tissue for applications where long-term stability of the hydrogel is required. The hydrogel is reinforced with cellulose nanofibers extracted from the Ciona intestinalis sea invertebrate followed by double chemical and photochemical crosslinking. The hydrogel is additionally loaded with dexamethasone to provide sustained anti-inflammatory activity. The reinforced double-crosslinked hydrogel after drug loading maintained high optical transparency with significantly improved mechanical characteristics compared to non-reinforced hydrogels, while supporting a gradual sustained drug release for 60 days in vitro. Dexamethasone, after exposure to crosslinking and sterilization procedures used in hydrogel production, inhibited tube formation and cell migration of TNFα-stimulated vascular endothelial cells. The drug-loaded hydrogels suppressed key pro-inflammatory cytokines CCL2 and CXCL5 in TNFα-stimulated human corneal epithelial cells. Eight weeks after intra-stromal implantation in the cornea of 12 New-Zealand white rabbits subjected to an inflammatory suture stimulus, the dexamethasone-releasing hydrogels suppressed TNFα, MMP-9, and leukocyte and fibroblast cell invasion, resulting in reduced corneal haze, sustained corneal thickness and stromal morphology, and reduced overall vessel invasion. This collagen-nanocellulose double-crosslinked hydrogel can be implanted to treat corneal stromal disease while suppressing inflammation and maintaining transparency after corneal transplantation. Statement of significanceTo treat blinding diseases, hydrogel scaffolds have been proposed to facilitate corneal restoration and ocular drug delivery. Here, we improve on a clinically tested collagen-based scaffold to improve mechanical robustness and enzymatic resistance by incorporating sustainably sourced nanocellulose and dual chemical-photochemical crosslinking to reinforce the scaffold, while simultaneously achieving sustained release of an incorporated anti-inflammatory drug, dexamethasone. Evaluated in the context of a corneal disease model with inflammation, the drug-releasing nanocellulose-reinforced collagen scaffold maintained the cornea's transparency and resisted degradation while suppressing inflammation postoperatively. This biomaterial could therefore potentially be applied in a wider range of sight-threatening diseases, overcoming suboptimal administration of postoperative medications to maintain hydrogel integrity and good vision.

Near-infrared photothermal dual crosslinking strategy for precise and efficient direct ink writing of high solids ceramic slurries

During the ceramic photocuring 3D printing process, the penetration ability of incident light is hindered by the extinction effects of ceramic powders in ceramic slurry. This limitation in light penetration negatively impacts printing efficiency, especially in ceramic slurries with high solid contents. In this work, an in-situ photothermal dual crosslinking strategy, which capitalizes on the combined benefits of near-infrared photothermal energy, was proposed to realize precise and efficient direct ink writing of high solids ceramic slurries. The in-situ curing of ceramic slurries with an alumina content of up to 90 wt% (74.5 vol%) was successfully achieved by integrating photochemical and photothermal crosslinking strategies to recycle excess heat to enhance the energy utilization of near-infrared light. Under near-infrared irradiation (538.25 W/cm2, 3 s), the high solids ceramic photothermal dual curing slurry achieved a curing depth of 2.79 mm, which improved the printing rate and printing throughput compared with the photocuring slurry (2.34 mm) and the thermocuring slurry (0.98 mm). The sintered samples showed a sinter shrinkage of 8.85 % and relative density of 95.08 %. This method has great potential for application in the manufacturing of thick composite materials and high solid content slurry printing.

Effect of intragranular/extragranular tara gum on sustained gastrointestinal drug delivery from semi-IPN hydrogel matrices

The present research was undertaken to develop semi-IPN hydrogel matrix tablets of tara gum (TG) and carboxymethyl TG (CMTG) for sustained gastrointestinal delivery of highly water soluble tramadol hydrochloride (TH). The matrix tablets were developed by a hybrid process of wet granulation and direct compression technique. Carboxymethyl TG was crosslinked with dual cross-linking ions (Al3+/Ca2+). The uncross-linked component of the semi-IPN matrix was either incorporated within the granules (intragranular TG) or incorporated outside the granules (extragranular TG), prior to compression. The effect of intragranular/extragranular TG on the swelling, erosion and TH release characteristics from the semi-IPN hydrogel matrix tablets was investigated. The key finding of the investigation indicated that intragranular TG expedited TH release, while extragranular TG sustained TH release. Moreover, the effect of cross-linking ions on viscosity, rigidity, cross-link density and TH release behavior from hydrogel matrices was investigated. In-vivo pharmacokinetic performance of the optimized extragranular TG semi-IPN hydrogel matrix (F15) indicated sustained TH release in gastrointestinal milieu.