Double Crosslinking Research Articles

Cu-Fe3O4/sodium alginate/polyacrylamide hydrogel evaporator for solar seawater desalination

As an environmentally friendly seawater desalination method, solar interface evaporation is considered to be a promising solution to ease the freshwater shortage. In this paper, porous Cu-Fe3O4/sodium alginate/polyacrylamide hydrogel was prepared by double chemical crosslinking method using sodium alginate, polyacrylamide and Cu-Fe3O4 nanoparticles with good SPR effect as raw materials. The effects of Cu-Fe3O4 nanoparticle concentration, light intensity and salt water concentration on the evaporation performance of hydrogel evaporator were studied. It was found that under the light intensity of 1 sun, the evaporation efficiency and thermal efficiency of 3.5 wt% seawater in the hydrogel evaporator containing Cu-Fe3O4 nanoparticles with a concentration of 0.26% can reach 64.7% and 95.24%, respectively. In addition, the Cu-Fe3O4/sodium alginate/polyacrylamide hydrogel evaporator has good reusability and salt self-cleaning ability. The seawater desalination experiment in real environment shows that the hydrogel evaporator with low cost benefit has broad application prospects in the field of seawater desalination.

Double-crosslinked hydrogels and hydrogel beads formed by garlic protein hydrolysates for bioactive encapsulation and gastrointestinal delivery.

Garlic protein is one of the main components of garlic. It has several beneficial characteristics. This study aimed to characterize a double crosslinked hydrogel formed with alginate, calcium ions (Ca2+), and garlic protein hydrolysates (GPH), and to develop hydrogel beads for targeted delivery of bioactive constituents to the gastrointestinal tract. The results indicated that the degree of GPH hydrolysis was approximately 3% following trypsin treatment. The inner structure of the double crosslinked hydrogel showed a honeycomb pattern, with solid-like gel rheology and improved texture properties at a 4% (w/v) GPH concentration. The GPH-based hydrogel beads demonstrated pH sensitivity, swelling in near-neutral and alkaline environments, and the encapsulated paclitaxel (PTX) exhibited an amorphous phase with preferential release in intestinal conditions. The GPH group also achieved greater drug encapsulation efficiency than a soy protein hydrolysate (SPH) group, and proteomic analysis suggested that lower molecular weight and peptide charge favored the formation of peptide-integrated double crosslinking hydrogels. This work indicated that GPH was helpful and could inspire the development of drug delivery systems involving GPH with the required mechanical strength and target-release properties. © 2024 Society of Chemical Industry.

Enhanced physicochemical properties and riboflavin 7 delivery ability of soy isolate protein/sugar beet pectin composite freeze-dried gels prepared by double crosslinking strategy

Enhanced physicochemical properties and riboflavin 7 delivery ability of soy isolate protein/sugar beet pectin composite freeze-dried gels prepared by double crosslinking strategy

Sunflower pith inspired dual-gradient cellular polyurethane architecture with amplified mechanical functions

Artificial cellular materials with various mechanical functions are attracting increasing attentions from aerospace, transportation, and industrialization. However, many artificial cellular materials, despite of the hierarchically ordered structures and even unique performance to some, still lag behind many natural ones in amplification of mechanical functions owing to the limitations in intrinsic mechanical performance and sophisticated structural design. Herein, inspired with lightweight and high strength of sunflower piths, we proposed a dual-gradient structure consisting of pore size gradient and wall thickness gradient to engineer cellular architectures with desirable mechanical performance by harnessing vat photopolymerization 3D printing of double crosslinking networks polyurethane elastomer. The double-gradient cellular polyurethane architecture displays more exceptional capability in load-bearing and energy absorption compared with non– and single gradient structures. Besides, the specific compressive strength and energy absorption of the dual-gradient cellular architectures are 4 times higher than those of traditional mechanical metamaterial structures such as octet-truss lattice, gyroid lattice, and porous structure prepared with the same material. Potential mechanisms such as dual-gradient cellular structures to obtain selective flexural deformation behaviour increasing their energy absorption and dissipation capacity are fully elucidated. As the potential paradigms, we demonstrated the mechanical functions of biomimetic mechanical cellular architectures for efficient impact protection and noise isolation, which offered a promising perspective toward developing soft metamaterials with excellent mechanical functions for potential soft machines and engineering applications.

A MnO2 nanosheets doping double crosslinked hydrogel for cartilage defect repair through alleviating inflammation and guiding chondrogenic differentiation

The inflammatory microenvironment and inferior chondrogenesis are major symptoms after cartilage defect. Although various modifications strategies associated with hydrogels exhibit remarkable capacity of pro-cartilage regeneration, the adverse effect by prolonging inflammation is still formidable to hamper potential biomedical applications of different hydrogel implants. Herein, inspired by the repair microenvironment of articular cartilage defects, an injectable, immunomodulatory, and chondrogenic L-MNS-CMDA hydrogel is prepared through grafting vinyl and catechol groups to chitosan macromolecules using amide reaction, then further loading MnO2 nanosheets (MNS). The double crosslinking of photopolymerization and catechol oxidative polymerization endows L-MNS-CMDA hydrogel with preferable mechanical property, affording a suitable mechanical support for cartilage defect repair. Additionally, the robust tissue adhesion capability stemming from catechol groups guarantees the long-term retention of the hydrogel in the defect site. Meanwhile, L-MNS-CMDA hydrogel decomposes exogenous and intracellular H2O2 into O2 and H2O, to effectively alleviate cellular oxidative stress caused by long-term hypoxia. Under the synergies of catechol groups and MNS, L-MNS-CMDA hydrogel not only inhibits macrophages polarizing into M1 phenotype, but encourages them turn into M2 phenotype, thereby, reconstructing an immunization friendly microenvironment to ultimately enhance cartilage regeneration. Predictably, the hydrogel markedly induces rat bone marrow mesenchymal stem cells differentiating into chondrocytes by expressing abundant glycosaminoglycan and type II collagen. A cartilage defect model of rat knee joint indicates that L-MNS-CMDA hydrogel visually regulate the early inflammatory response of post-implantation, and facilitate cartilage regeneration and recovery of joint function after 12 weeks of post-implantation. All in all, this multifunctional L-MNS-CMDA hydrogel exhibits superior immunomodulatory and chondrogenic properties, holding immense clinical potential in the treatment of cartilage defects.

Direct Synthesis of Artificial Esterase through Molecular Imprinting Using a Substrate-Mimicking Acylthiourea Template.

Most reported artificial esterases hydrolyze only activated esters. We here report a one-pot synthesis of artificial esterases via molecular imprinting. An acylthiourea template hydrogen bonds with 4-vinylbenzoic acid and coordinates to a polymerizable zinc complex inside a cross-linkable surfactant micelle. Double cross-linking of the micelle yields a polymeric nanoparticle catalyst that mimics a metalloenzyme to activate a water molecule for nucleophilic attack on the bound ester. The catalyst hydrolyzes both activated and unactivated esters under mild conditions with selectivity.

Double cross-linked biomass aerogels with enhanced mechanical strength and flame retardancy for construction thermal insulation

Biomass aerogels are expected to be a popular material in construction field due to their sustainability, eco-friendliness and excellent thermal insulation properties. In this paper, high modulus biomass aerogels based on the principle of double cross-linking of physics and chemistry were synthesized by freeze-drying technique using gelatin, sodium carboxymethyl cellulose, glutaraldehyde, phytic acid and diatomite as raw materials. The presence of a double cross-linked network structure endowed the prepared aerogels with a low thermal conductivity (0.021–0.029 W·m−1·k−1). The density of only 0.0865 g·cm−3 biomass aerogel exhibited an extrastrong compression modulus of 31.5 MPa, which was superior to common biomass aerogels. Biomass intumescent flame retardant system composed of sodium carboxymethyl cellulose (carbon source), gelatin (gas source) and phytic acid (acid source) was used in combination with diatomite to enhance flame retardancy (limit oxygen index value up to 36.5 %, UL-94 V-0 rating and total smoke production reduced from 0.31 m2 to 0.18 m2) and thermal stability (the residue up to 48.91 %). Remarkably, the modified aerogel showed incredible hydrophobicity (hydrophobic angle of 137°). In summary, the results indicated this study proposed a novel green idea for the preparation of construction thermal insulation materials with a combination of high modulus, flame retardancy and hydrophobicity.

Dual-continuous microneedle patch integrating transdermal delivery of pH-sensitive licorzinc MOFs and Zn2+ hydrogel sensors for treating alopecia areata

Licorzinc is a commonly used immunomodulator, but faces poor water solubility, high oral dose, and side effects of zinc accumulation by long-term administration. Herein, a new licorzincform was developed by adsorbing glycyrrhizic acid (GA) into zeolitic imidazolate framework-8 (GA@ZIF-8) with superior solubility and acid-responsive drug release properties. Then, a dual-continuous microneedle patch was developed for simultaneous transdermal delivery of GA@ZIF-8 and monitoring Zn2+ in local tissues, where dissolving microneedles as a drug delivery unit were fabricated from hyaluronic acid. In contrast, swollen hydrogel microneedles as a diagnostic unit were prepared from double cross-linking of N-acryloyl-glycinamide and α-methylacrylic acid and hybridized with Eu3+ and terpyridine (TPy). The microneedles for transdermal GA@ZIF-8 delivery were completely dissolved in 2 min, which improved the cyclophosphamide-induced hair follicle recession in mice by reducing CD8+NKG2D+ T cells infiltration, inhibiting Jak receptor activation, and decreasing IL-15 and IFN-γ. Additionally, as a sensor unit, the microneedles rapidly absorbed water swelled when stabbed into the skin, and fluoresced red when exposed to 365 nm light. Zn2+ in the inter tissue fluid competes with Eu3+ in the TPy-Eu3+ complex and coordinates with Tpy, which triggers a change in fluorescence. Notably, the detection Zn2+concentration range was 10–8 M–10–1 M, and it was not disturbed by metal ions including Na+, K+, Mg2+, and Ca2+, suggesting that it is competent to be applied as a real-time chemosensor of Zn2+. Collectively, this newly designed system with both therapeutic and diagnostic functions provides a new strategy for treating zinc-related diseases.

Preparation and performance study of GLC/TMP double crosslinking modified waterborne polyurethane for wood coatings

Preparation and performance study of GLC/TMP double crosslinking modified waterborne polyurethane for wood coatings

Antibacterial and antioxidative hydrogel dressings based on tannic acid-gelatin/oxidized sodium alginate loaded with zinc oxide nanoparticles for promoting wound healing

Wound infection resulting in delayed wound healing and wound deterioration remains a clinical challenge. Recently, multifunctional hydrogel dressing was a promising strategy which has attracted wide attention in preventing wound infection and promoting wound healing. In this study, a hybrid hydrogel made of gelatin (GL), tannic acid (TA), oxidized sodium alginate (OSA), and zinc oxide nanoparticles (ZnO NPs) was prepared mainly by double network cross-linking approach, named tannic acid-gelatin/oxidized sodium alginate/zinc oxide (TA-GL/OSA/ZnO). The composite hydrogels exhibited improved mechanical properties, which provided by TA modified the structure of GL network, Schiff base reaction between GL and OSA, and the strengthening effect of ZnO NPs. Meanwhile, the composite hydrogel showed high antibacterial activity against Staphylococcus aureus (S. aureus) (97.8 % ± 0.9 %) and Escherichia coli (E. coli) (96.6 % ± 1.2 %), attributed to the synergistic effect of TA and ZnO NPs. Furthermore, benefiting from the good antioxidative properties of TA, the sustain-released Zn2+ with the good capability to kill bacteria, and promoting the regeneration of skin epithelial tissues in BALB/c mice constantly, the multifunctional hydrogel had a significant therapeutic effect on wound healing and broad application prospects.

Huge improved gas separation performance of carbon molecular sieve membrane by forming a double crosslinked polyimide precursor

A vital issue in searching for advanced gas separation membranes is understanding the precursor structure-gas separation properties of carbon molecular sieve (CMS) membranes. Here, we reported two crosslinked polyimides and used as CMS precursors, in which, the DCPI-4 is a double cross-linkable polyimide with 4 % triptycene triamine as a crosslinker (Type I) and COOH group that can be crosslinked at 350 °C by decarboxylation (Type II), whereas the DCPI-0 with COOH (Type II). After pyrolysis at 550 °C, the DCPI-4-CMS showed a higher SBET (812 vs 713 m2g-1), larger ultra-microporosity ratio (26.6 % vs 17.8 %), larger d-spacing (4.08 vs 3.94 Å), less graphitization (sp3/sp2 of 0.156 vs 0.118), 5.5 times higher CO2 permeability (7573 vs 1391 Barrer) and same CO2/CH4 selectivity (∼62) than DCPI-0-CMS. We consider this is due to the type I crosslinking enhances the rigidity of the polyimide backbone, and inhibits the collapse of micropores during the carbonization, which causes improved ultra-microporosity and ultra-micropore ratio that both enhances the gas diffusion and solubility coefficient as well activation energy difference of gas pairs. Conclusively, this double crosslinking method provides a good perspective for achieving CMS membranes with excellent gas separation performance.

Double cross-linking system for constructing tortuosity-lowered and strength-enhanced porous MXene films with superior capacitive performance and electromagnetic shielding efficiency

Porous MXene films are ideal materials for flexible electronics because of their various porous structures and rich surface chemistry. However, the typical problem, especially as flexible supercapacitors, is that MXene lamellae are still prone to stacking. Many channels are disconnected from each other, facing high ion transport resistance. Herein, an optimal 3D structure is built by ion-molecular double cross-linking system and subsequent freeze-casting with lowered-tortuosity and enhanced-strength for porous MXene films. Ionic cross-linking is used to adjust the orientation of the MXene lamellae by coulombic attraction, while optimized terminal and ion intercalation widens the layer spacing. Molecular cross-linking is used to adjust the backbone of the porous structure through hydrogen bonding interactions. As a result, due to the porous structure of connectivity, the porous MXene-OH/BC (MOB) delivers a capacitance of 527 F g-1, mechanical property of 41.5 MPa (140 % and 367 % of the MXene film, respectively), and the shielding efficiency of 67.2 dB (X-bond). In addition, the assembled NAC//MOB device achieves high energy density of 56.28 Wh kg-1 and 85.6 % capacitance retention after 50,000 cycles. This work shows a well-designed porous film with lightweight, flexible and strong mechanical properties, expanding the competitiveness of MXene materials for real-world applications.

Interfacial Wrinkling Structures Based on a Double Cross-Linking Strategy Enable a Dual-Mode Optical Information Encryption.

Surface wrinkling structures based on a bilayer system are widely employed in storing and encrypting specific optical information. However, constructing a stable wrinkling structure with high-level security remains an extensive challenge due to the delamination issue between the skin layer and the substrate. Herein, a double cross-linking strategy is introduced between a hydrogel layer doped with fluorescent molecules and polydimethylsiloxane to establish a stable interfacial wrinkling structure with dual-mode functionality, in which the light reflection of the wrinkles and fluorescence intensity of fluorescent molecules can be simultaneously regulated by the modulus ratio between the two layers. The spontaneous wrinkling structures with a physically unclonable function can enhance the photoluminescence emission intensity of the wrinkling area under ultraviolet radiation. Meanwhile, the skin layer constructed of acrylamide and acrylic acid copolymer protects the interfacial wrinkling patterns from the loss of a detailed structure for authentication due to external damage. The stable interfacial wrinkling structures with fluorescence can find potential applications in the fields of information storage and encryption.

Reconstruction of zinc-metal battery solvation structures operating from −50 ~ +100 °C

Serious solvation effect of zinc ions has been considered as the cause of the severe side reactions (hydrogen evolution, passivation, dendrites, and etc.) of aqueous zinc metal batteries. Even though the regulation of cationic solvation structure has been widely studied, effects of the anionic solvation structures on the zinc metal were rarely examined. Herein, co-reconstruction of anionic and cationic solvation structures was realized through constructing a new multi-component electrolyte (Zn(BF4)2-glycerol-boric acid-chitosan-polyacrylamide, simplified as ZGBCP), which incorporates double crosslinking network via the esterification, protonation and polymerization reactions, thereby combining multiple advantages of ‘liquid-like’ high conductivity, ‘gel-like’ robust interface, and ‘solid-like’ high Zn2+ transfer number. Based on the ZGBCP electrolyte, the Zn anodes achieve record-low polarization and stable cycling. Furthermore, the ZGBCP electrolyte renders the AZMBs ultrawide working temperature (−50 °C ~ +100 °C) and ultralong cycle life (30000 cycles), which further validates the feasibility of the dual solvation structure strategy and provides a innovative perspective for the development of high-performance AZMBs.

Pectin film fortified with zein nanoparticles and Fe3+-Encapsulated propolis extract for enhanced fruit preservation

In this study, pectin served as the film matrix while propolis extract (PPE) acted as both an antibacterial agent and antioxidant. Utilizing the encapsulation of zein nanoparticles and cross-linking of Fe3+ with pectin molecules, a dual encapsulation system of PPE in the pectin film was successfully achieved, resulting in antibacterial and antioxidant pectin films. The effects of incorporating PPE, zein, and Fe3+ on various properties of the pectin films were investigated. Additionally, the impact of zein nanoparticle encapsulation and Fe3+ dual encapsulation systems on the release characteristics of PPE in the pectin films was examined. Characterization techniques including FTIR, SEM, XRD crystal diffraction, and thermogravimetric analysis were employed to analyze the interactions, microstructure, crystal structure, and thermal stability of the films. The results showed that the double cross-linking of zein and Fe3+ led to a reduction in the moisture content of the pectin film by approximately 46%, a decrease in water vapor permeability by about 19%, an almost doubling of tensile strength and antioxidant activity, and a significant improvement in antibacterial properties. Additionally, the incorporation of zein and Fe3+ enhanced the release characteristics of PPE in the pectin films. Notably, the developed composite coating demonstrated improved preservation properties during the storage of strawberry fruits.

High water resistance starch based intelligent label for the freshness monitoring of beverages

The traditional starch-based intelligent freshness labels struggle to maintain long-term structural stability when exposed to moisture. To solve this problem, we prepared composite crosslinked labels using phytic acid for double crosslinking of corn starch and soybean isolate proteins, with anthocyanin serving as the chromogenic dye. The mechanical properties, hydrophobic characteristics, and pH responsivity of these crosslinked labels were assessed in this study. The prepared double-crosslinked labels showed reduced moisture content (15.96%), diminished swelling (147.21%), decreased solubility (28.55%), and minimized water permeability, which suggested that they have enhanced hydrophobicity and densification. The crosslinked labels demonstrated the ability to maintain morphological stability when immersed in water for 12 h. Additionally, the mechanical properties of the crosslinked labels were enhanced without compromising their pH-sensing capabilities, demonstrated a color response visible to the naked eye for milk and coconut water freshness monitoring, suggesting great potential for application in beverages freshness monitoring.

Development of boiling water resistance starch-based wood adhesive via Schiff base crosslinking and air oxidation strategy

Starch adhesives are promising biomass adhesives. However, their polyhydroxy structure leads to poor water resistance. In this study, DAS-HBP adhesive with a densely cross-linked structure was prepared by reacting dialdehyde starch (DAS) with hyperbranched polyamide (HBP) via the Schiff base. In order to increase the water resistance, glucose was introduced for secondary cross-linking to obtain DAS-HBP-G adhesive with a double cross-linked structure. The cross-linking mechanism of glucose and DAS-HBP was investigated by FTIR, XPS, LC-MS, and 13C NMR. Glucose was oxidized to various aldehyde structures under heating conditions to provide sufficient reactive groups for secondary cross-linking. The introduction of glucose not only reduced the curing temperature of the adhesive and enhanced its thermal stability but, most importantly, substantially enhanced its water resistance. The wet strength of DAS-HBP was 0.72 and 0.67 MPa, respectively, while DAS-HBP-G reached 1.26 and 1.15 MPa. The excellent water resistance is attributed to the synergistic effects of the internal hyperbranched structure of the adhesive, hydrogen bonding, imide, and amide bonding. This double cross-linking strategy provides a potential approach for the development of water-resistant starch adhesives.

A bioactive composite sponge based on biomimetic collagen fibril and oxidized alginate for noncompressible hemorrhage and wound healing

The study focuses on developing a bioactive shape memory sponge to address the urgent demand for short-term rapid hemostasis and long-term wound healing in noncompressible hemorrhage cases. A composite sponge was created by spontaneously generating pores and double cross-linking under mild conditions using biomimetic collagen fibril (BCF) and oxidized alginate (OA) as natural backbone, combined with an inert calcium source (Ca) from CaCO3-GDL slow gelation mechanism. The optimized BCF/OACa (5/5) sponge efficiently absorbed blood after compression and recovered to its original state within 11.2 ± 1.3 s, achieving physical hemostatic mechanism. The composite sponge accelerated physiological coagulation by promoting platelet adhesion and activation through BCF, as well as enhancing endogenous and exogenous hemostatic pathways by Ca2+. Compared to commercial PVA expanding hemostatic sponge, the composite sponge reduced bleeding volume and shortened hemostasis time in rat liver injury pick and perforation wound models. Additionally, it stimulated fibroblast migration and differentiation, thus promoting wound healing. It is biodegradable with low inflammatory response and promotes granulation tissue regeneration. In conclusion, this biocomposite sponge provides multiple hemostatic pathways and biochemical support for wound healing, is biologically safe and easy to fabricate, process and use, with significant potential for clinical translation and application.

Carbene-mediated gelatin and hyaluronic acid hydrogel paints with ultra adhesive ability for arthroscopic cartilage repair

In articular cartilage defect, particularly in arthroscopy, regenerative hydrogels are urgently needed. It should be able to firmly adhere to the cartilage tissue and maintain sufficient mechanical strength to withstand approximately 10 kPa of arthroscopic hydraulic flushing. In this study, we report a carbene-mediated ultra adhesive hybrid hydrogel paints for arthroscopic cartilage repair, which combined the photo initiation of double crosslinking system with the addition of diatomite, as a further reinforcing agent and biological inorganic substances. The double network consisting of ultraviolet initiated polymerization of hyaluronic acid methacrylate (HAMA) and carbene insertion chemistry of diazirine-grafted gelatin (GelDA) formed an ultra-strong adhesive hydrogel paint (H2G5DE). Diatomite helped the H2G5DE hydrogel paint firmly adhere to the cartilage defect, withstanding nearly 100 kPa of hydraulic pressure, almost 10 times that in clinical arthroscopy. Furthermore, the H2G5DE hydrogel supported cell growth, proliferation, and migration, thus successfully repairing cartilage defects. Overall, this study demonstrates a proof-of-concept of ultra-adhesive polysaccharide hydrogel paints, which can firmly adhere to the articular cartilage defects, can resist continuous hydraulic pressure, can promote effective cartilage regeneration, and is very suitable for minimally invasive arthroscopy.

Unlocking plateau capacity with versatile precursor crosslinking for carbon anodes in Na-ion batteries

As the precursor material inherently determines the fundamental structure of hard carbons, a direct manipulation of precursors at the molecular level promises enhanced flexibility in designing hard carbon architectures, which plays a pivotal role in dictating the final microstructural properties and, ultimately, the overall sodium storage performance. In this study, we present a novel generalized strategy utilizing P and O double cross-linking to convert pitch into a thermosetting precursor, creating copious micropores within pitch-based carbon. These micropores serve as essential pathways and active binding sites for sodium ion transport and storage, leading to pitch-derived hard carbons with a remarkable specific capacity of 416.1 mAh/g and an impressive initial Coulombic efficiency of 89.7%. Extensive study revealed a strong correlation between the increased plateau capacity and the closed pore volume, validating the micropore-driven sodium ion storage mechanism. Our findings underscores the groundbreaking significance of cross-linking in precursor modification, paving the way for the design and synthesis of high-performance hard carbon anodes for next-generation Na-ion batteries.