Cross-linked Structure Research Articles

Dynamic silicone hydrogel gauze coatings with dual anti-blood adhesion mechanism for rapid hemostasis and minimal secondary damage.

Hemostatic materials that can rapidly control bleeding without causing secondary damage or sharp pain upon removal are receiving increasing demands in acute trauma treatments and first-aid supplies. Here, we report the development of a dynamic silicone hydrogel coating on medical gauze to enable rapid hemostasis and synergistic anti-blood adhesion properties. The silicone hydrogel can spontaneously form oriented cross-linked structures on fibrous medical gauze through a solution-processing method to achieve macroscopic superhydrophobicity with microscopic surface slipperiness, resulting in excellent anti-blood adhesion with the on-wound peeling force at ~0 millinewton. The development of dynamic silicone hydrogel coating on medical gauze enables a unique integration of advanced features including instant bleeding control, excellent anti-blood adhesion, and excellent air permeability. The proposed strategy is also suitable for scalable production, making it promising in the applications of trauma management.

Facile sponge-like chitosan capsules as efficient adsorbent for anionic Congo red, Reactive brilliant blue KNR, and Methyl blue dyes: Performance and mechanism

In this study, sponge-like chitosan capsules (CTS-S) were successfully prepared as efficient adsorbent through a facile and green method. The cross-linked porous structure and abundant adsorption sites of CTS-S led to stable and remarkable adsorption efficacy for the purification of wastewater containing anionic dyes in a wide pH range. The highest maximum adsorption capacity for Congo red (CR), Reactive brilliant blue KN-R (KNR), and Methyl blue (MB) were 1372.49, 881.75, and 169.04mg/g, respectively. Kinetics study suggested that KN-R and CR adsorption processes were best depicted by the PSO model, while PFO model was applicable for MB. Adsorption isotherms of CR, KNR, MB conformed to the Sips model, demonstrating that the adsorption of CR, KNR, MB onto CTS-S was monolayer and heterogeneous. Adsorption mechanism insights further verified that electrostatic forces, hydrogen bonds, and n-π stacking worked for efficient removal of CR, KNR, MB by CTS-S, which was supported by characterization results and DFT calculation. Overall, CTS-S provided a useful and promising option as low-cost and eco-friendly absorbents for the adsorption of synthetic dyes.

Closed-loop recylcing of thermoset poly(vinylogous urethane) foams

Foams are an intriguing class of porous and lightweight materials which have found widespread applications in thermal insulation, pollutant adsorption, catalyst support, and energy storage. However, their covalently cross-linked structure makes foam unable to be recycled resulting in serious environmental burden. To address this challenge, we report the first example of closed-loop chemically recyclable foam. A simple, catalyst-free cryo-polymerization process with multifunctional amines and acetoacetates was utilized to successfully prepare a series of poly(vinylogous urethane) foams, containing dynamic covalent bonds which can selectively be cleaved on demand. The resulting foams exhibit macroporous structure with diameters exceeding 14 μm, pronounced thermal stability (Td,5% > 262.5 °C), robust hydrophobicity (WCA > 93°) and unique reactivity. Applications have been demonstrated for efficient adsorption of organic solvents and anionic dyes. More importantly, the foams show excellent recyclability under acidic conditions with high monomer recovery yields of up to 97 % and high purity levels. Fresh foams could be regenerated from the retrieved building blocks, thus demonstrating efficient closed-loop recycling. This work provides a new “monomer-foam-monomer” ecological chain and may inspire the advancement of next-generation closed-looped recyclable foam materials.

Hybrid dynamically cross-linked polyurethanes with room temperature self-healing ability for light-responsive actuator

Light-responsive actuators (LRAs) with cross-linked networks that demonstrate fast response and super mechanical strength are essential for practical applications. However, the permanent cross-linked structure typically stabilizes polymer networks and makes them difficult to reprogram or self-heal. Herein, a novel crosslinked light-responsive polyurethane actuator (CPU-DA1SS2) with room temperature self-healing properties was prepared by constructing a hybrid physical and chemical cross-linked polymer network via dynamic DA bonds, SS bonds, and hydrogen bonds. The CPU-DA1SS2 light-responsive actuator exhibits high tensile strength (25.52 MPa) and excellent self-healing efficiency (90.16 %) at room temperature. Moreover, the hybrid dynamic cross-linked network endows the LRAs with liquid-state remold ability and solid-state plasticity, which further contributes to diverse 3D geometric shape remolding. Such a hybrid, dynamic, cross-linked strategy could be utilized to design smart materials that are self-healing and recyclable without sacrificing their mechanical properties, helping to broaden the application areas of LRA materials.

Photochemical and Collision-Induced Cross-Linking of Asp, Glu, Asn, and Gln Residues in Peptide-Nitrile Imine Conjugate Ions in the Gas Phase.

Peptide conjugates furnished with a 2,5-diaryltetrazolecarbonyl tag at the C-terminal lysine, which we call peptide-tet-K, were found to undergo efficient cross-linking of Asp, Glu, Asn, and Gln residues to transient nitrile-imine intermediates produced by photodissociation and collision-induced dissociation (CID) of the tetrazole ring in gas-phase ions. UV photodissociation (UVPD) at 213 nm achieved cross-linking conversion yields of 37 and 61% for DAAAK-tet-K and EAAAK-tet-K, respectively. The yields for NAAAK-tet-K and QAAAK-tet-K were 29 and 57%, respectively. Even higher cross-link yields were found for CID-MS3 of stable denitrogenated ions, (peptide-tet-K-N2 + H)+, that were in the 69-83% range. Different types of cross-links were distinguished by CID-MSn that showed a distinct series of backbone fragment ions, loss of N-terminal groups, and loss of phenylhydrazine from the modified nitrile imines. The Asp and Glu side-chain carboxyl groups were major participants in cross-linking that resulted in proton and oxygen transfer to the nitrile imine group. Other types of cross-linking involved Asn and Gln CONH2 groups and backbone amides. Cyclic ion mobility-mass spectrometry was used to separate NAAAK-tet-K and QAAAK-tet-K conformers and products of their collision-induced denitrogenation. Linear nitrile-imine and cross-linked ion structures were identified by comparing the experimental collision cross sections (CCSexp) to those for structures obtained by combined Born-Oppenheimer molecular dynamics and density functional theory (DFT) calculations. The formation of cross-links was found to be energetically favorable and involved proton-facilitated nucleophilic attack at the nitrile-imine carbon atom.

Rheological and thermal property of KH570-modified nano-SiO2 grafted xanthan gum and its application in drilling fluid system

Xanthan gum (XG), recognized for its environmentally friendly properties and versatile capabilities, has been studied for drilling fluid applications. However, its limited solubility and thermal stability restricts its broader use. In this study, a modified XG derivative, XG-g-KH570 modified SiO2, was synthesized by grafting XG with KH570-modified nano-SiO2. The modified product exhibited lower molecular weights with Mn and Mw of 3.00 × 105 g/mol and 3.77 × 105 g/mol, respectively. Its pyruvate and acetyl contents decreased to 2.72 % and 1.68 %, respectively. Meanwhile, XG-g-KH570 modified SiO2 showed a higher branching degree of 45.3 % based on methylation analysis. In terms of performance, XG-g-KH570 modified SiO2 exhibited improved water solubility. XG-g-KH570 modified SiO2 demonstrated superior high-temperature and high-salinity performance, retaining high viscosity retention and viscoelasticity. Additionally, XG-g-KH570 modified SiO2 exhibited a markedly reduced fluid loss of only 3.4 mL at 150 °C, compatible with conventional desulphonated drilling fluids. Furthermore, its high-temperature thickening and fluid loss control mechanisms was found to be associated with an enhanced cross-linked network structure based on the zeta potential and particle size distribution under high-temperature and salinity conditions. These results represent a promising advancement in the field of biomolecular drilling fluid additives, providing an efficient and eco-friendly solution for the oil and gas industry.

Green synthesis of starch/chitosan complex via ozone-mediated Schiff reaction: Structure, thermal behaviors and surface properties

Ozone was used as a green and environmentally friendly initiator to directly induce a Schiff base cross-linking reaction between chitosan and waxy rice starch (CS) in the present investigation. The effects of oxidation on the structure of chitosan/starch bio-based composite, along with the cross-linked structure formation via Schiff base reaction, were investigated and confirmed using FTIR, XRD, and XPS characterization techniques. The formation of new bonds (C=N) along with other attributes imparted by the cross-linking reaction were evaluated and characterized. Notably, the ozone-induced cross-linking reaction significantly altered the water retention capabilities of CS, especially in the case of aqueous ozone treatment, which significantly improved its swelling power, water holding capacities, and water adsorption. Additionally, aqueous ozone treatment facilitated the formation and stabilization of the gel network. Gaseous ozone in dry state proved more effective in promoting the formation of CN groups, leading to enhanced surface hydrophobicity, while aqueous ozone offered better oxidation uniformity for the coexistence system of chitosan and starch. This work provides a novel and environmentally friendly approach for fabricating the chitosan/starch chemically cross-linking materials through ozone-induced direct Schiff base reaction, which simplifies the preparation process of the complex and minimizing the utilization of solvents.

Preparation of sodium carboxymethyl cellulose/two-dimensional metal carbide composite xerogel by phytic acid crosslinking for uranium recovery

Uranium, as a raw material for clean and green energy, is abundant in the oceans. Therefore, uranium recovery from seawater is an important way to solve the problems of energy shortage and environmental pollution. Here, two-dimensional metal carbides (MXene) and sodium carboxymethyl cellulose (CMC) were crosslinked via phytic acid (PA) to prepare a composite xerogel with cross-linked network structure (PA@MCX). The results showed that PA@MCX had excellent wet-state strength (6.92 MPa) and recyclability, which were critical for adsorbent in practical applications. The adsorbent’s adsorption behavior was more aptly characterized by the pseudo-second-order kinetics and Langmuir isotherm model, yielding a theoretical maximum adsorption capacity of 468.5 mg/g. Furthermore, the phosphate groups in the PA@MCX adsorbent exhibited a strong preference for uranium, achieving a ratio of uranium to vanadium adsorption capacity of 6.6 in tests involving competing ions. After five adsorption–desorption cycles, the adsorbent can still maintain a high elution rate of 80.4 % for uranium. This gel-type adsorbent with high strength, easy recovery, considerable adsorption capacity and excellent selectivity will be one of the mainstreams for uranium extraction from seawater in the future.

Urinary pentosidine as a potential biomarker of muscle and physical performance in young adult men

Pentosidine is representative of the cross-linked structure of advanced glycation end products (AGEs) and has been suggested as a biomarker to assess bone and muscle quality. As studies on pentosidine in young adult men remain limited, we aimed to clarify the associations of urinary pentosidine with musculoskeletal status and physical performance in young men. Participants in this study comprised 32 men (age range: 19–39 years). Anthropometric measurements (body composition by InBody 430; stiffness index by ultrasound), muscle performance (grip strength by dynamometer, thigh muscle thickness by ultrasound), physical performance (functional reach test, 30-s chair stand test, and timed up and go test), and urinary biomarkers (pentosidine, N-telopeptide of type I collagen, and creatinine) were measured. In partial correlation analysis adjusted for age and height, higher urinary pentosidine levels were significantly associated with lower fat-free mass index (rho = − 0.368, p = 0.046), grip strength (rho = − 0.433, p = 0.017), rectus femoris thickness (rho = − 0.393, p = 0.032), and anterior thigh thickness (rho = − 0.416, p = 0.022), and a marginally inverse correlation was noted between urinary pentosidine levels and functional reach test (rho = − 0.327, p = 0.078). Our findings suggest that pentosidine correlates inversely with a few muscle and physical performance indicators. Pending future validations, urinary pentosidine may be a biomarker of AGEs in young men.

Feasibly Developing Polyester-Type Poly(vinyl alcohol) Adhesive in One Go with High Water Resistance and Bonding Performance.

Water-soluble poly(vinyl alcohol) (PVA) has great potential for the preparation of environmentally friendly adhesives. However, the application of PVA adhesives in the wood industry has been limited by their poor water and mildew resistance. Herein, a polyester-type PVA adhesive (CPVA) with good bonding performance, water resistance, and antimildew performance was synthesized using PVA and citric acid (CA). The cross-linking reaction, including esterification between PVA and CA chains and etherification between PVA chains, was demonstrated by Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Due to the cross-linked structure of the reaction, the CPVA1 (mass ratio of CA/PVA = 1:1) adhesive showed a low soluble content of 5% when it was soaked in water for 24 h. The dry strength, warm water (63 °C) strength, and hot water (93 °C) strength of the plywood hot-pressed from the CPVA1 adhesive at 200 °C were 1.06 1.52, and 1.45 MPa, respectively, which met the Chinese National Standard GB/T 9846-2015. The developed CPVA adhesive also adhered to glass and steel at room temperature. Therefore, the CPVA adhesive developed in this study can serve as a potential candidate for the production of nonformaldehyde wood-based composites with excellent bonding strength, water resistance, and mildew resistance.

A multifunctional carbon fiber composite film inspired by pumpkin growth toward tunable electromagnetic interference shielding

Carbon fiber composite film is an excellent electromagnetic interference (EMI) shielding material. However, its further application is limited by its single-loss characteristics of electromagnetic waves and unadjustable EMI shielding performance. Inspired by pumpkin growth, a carbon fiber/Co and Ni nanoparticles composite (PCF/CN) with porous, multi-interface, and cross-linked structure was designed through in-situ growth strategy in this work. In this process, Co2+ and Ni2+ were used as ovules while the composite nanofibers were used as the ovaries to provide active sites for seed growth. Polyether (P123) inside the composite nanofibers decompose under a high-temperature treatment and form a porous structure. The polyacrylonitrile (PAN) will form the "peel" during the high-temperature treatment. The PCF/CN provides abundant pores, plentiful non-homogeneous interfaces, and rich conduction paths for the attenuation of electromagnetic waves. After encapsulation with waterborne polyurethane (WPU), the obtained flexible PCF/CN/W composite film displays tunable EMI shielding efficiency using the "Origami" strategy. And the EMI shielding efficiency for PCF/CN-2/W reaches 24.73 dB after two folds due to the absorption loss, reflection loss, conduction loss, and interfacial polarization of the porous multi-interface cross-linked structure. Interestingly, the fabricated composite film also exhibits excellent photothermal conversion performance with fast thermal response time and stability. In addition, the resultant composite film processed sensitive sensing function to detect human joint motion.

Bioinspired Cholesteric Photonic Crystals with 3D Cross-Linked Network Structure for Humidity Sensors

Bioinspired Cholesteric Photonic Crystals with 3D Cross-Linked Network Structure for Humidity Sensors

Fluid Imbibing Super Absorbent Textiles for Comfort Wear Performance

Textile is a basic human need, it not only provides the aesthetic appeal but also imparts necessary sweat absorption and relevant functional effects. The textile material is widely used for various hygiene and comfort wear applications where the absorption as well as leak proof retention of various body fluids is an essential parameter. This effect is achieved when the textile material is treated with suitable super absorbent chemicals. Superabsorbent finishes are polymeric coatings that significantly enhance the liquid absorption capacity of textile substrates. Known as superabsorbent polymers (SAPs), these materials can be natural, synthetic, or hybrid, characterized by their high degree of cross-linking and three-dimensional network structure. Capable of absorbing up to 100,000% of their weight in water, SAPs form stable hydrogels due to their hydrophilic groups. These properties make them suitable for diverse applications, including hygiene products, water purification, horticulture, and pharmaceuticals. In the past few decades, super absorbent polymers and fibres have found a lot of applications, especially in the field of textiles. This report briefly discusses the various application fields of SAP in textiles. With applications in hygiene products, medical textiles, protective apparel, automotive textiles, and geotextiles, the study explores how SAPs are incorporated into textile fibres (SAFs) to improve moisture absorption and management. Lastly, a comprehensive outlook for the future is given, highlighting encouraging prospects in SAP-based textile research and industry.

Application of a Hessian-Based Image-Processing Method for Enhanced Visualization of Nanoscale Rubber Cross-Linked Network Structures from Electron Microscopy Images

Application of a Hessian-Based Image-Processing Method for Enhanced Visualization of Nanoscale Rubber Cross-Linked Network Structures from Electron Microscopy Images

Cross-linked structures reinforced the bamboo fiber/poly(lactic acid) composites with high heat resistance and their environmental impact through the life cycle assessment analysis

In order to prepare low-cost and heat-resistant poly(lactic acid) (PLA) composites, in this study, bamboo fiber (BF) was added to stereo-complex crystal PLA (SC-PLA) to prepare heat-resistant composites. Poly[(phenyl isocyanate)-co-formaldehyde] [a polyaryl polymethylene isocyanate (PAPI)] was used to form cross-linked structures between SC-PLA and BF, and the effects of PAPI-cross-linked structures on the crystallization properties, mechanical properties, and heat resistance of BF/SC-PLA composites with different BF contents were systematically investigated. When 15% BF was added, the mechanical properties of the composite were significantly improved. The tensile strength increased by 85.5% compared to the unmodified composite, reaching 34.7 MPa, which was even higher than that of the SC-PLA composite (33.1 MPa). In addition, in order to explore the impact of the PAPI-modified BF/SC-PLA composite on the environment and carbon emissions, a life cycle assessment (LCA) of the composites was conducted. The addition of BF effectively reduced the impact of the composite on the environment. Notably, the emissions of CO2 decreased by approximately 11.7%, and the freshwater, marine, and land ecotoxicity were also significantly reduced. This work provided a reference for the preparation of low-cost and heat-resistant PLA composites for heat-resistant food packaging and disposable tableware and expanded the application of PLA products in the field of heat-resistant materials.

How sorghum starch structural properties affect its resistance to cooking in baijiu brewing

The Chinese liquor baijiu is made from fermented sorghum grain. During fermentation, the cooking resistance (starch leaching rate) is an important factor for both baijiu producers and sorghum breeders, to select and breed suitable sorghum varieties. The factors and mechanisms which affect this resistance are not well understood. To investigate this, fifteen brewing sorghum varieties were used for brewing, with sampling over cooking time. The components, starch molecular structure and particle morphology of these samples were characterized and correlated with cooking parameters. In this study, high crystallinity and gelatinization enthalpy in sorghum grains were found to reduce cooking resistance by enhancing swelling power to break the seed coat and cell wall. This is the opposite of what happens in other cereal grains. High protein content, high particle size and high amylose content are the main factors for improving cooking resistance, which occurs by the formation of a cross-linked 3D structure and reduced water absorption to inhibit gelatinization. Both the average and the distribution of chain lengths of amylopectin and amylose are important factors affecting cooking resistance because, among other things, of their influence on crystal structure. This information might help manufacturers select and breed sorghum varieties which have optimal behavior for a given brewing method.

Smart Crowding on pH-Induced Elasticity of Weakly Anionic poly(N-Isopropylacrylamide)-Based Semi-Interpenetrating Polymer Networks via Integration of Methacrylic Acid and Linear Polyacrylamide Chains.

Weakly anionic semi-interpenetrating polymer networks (semi-IPNs), comprised of copolymer poly(N-isopropylacrylamide-co-methacrylic acid) P(NIPA-MA) and linear poly(acrylamide) (LPA) chains as macromolecular crowding agent, are designed to evaluate pH-induced swelling and elasticity. Uniaxial compression testing after swelling in various pH-conditions is used to analyze the compressive elasticity as a function of swelling pH and LPA-content. The swelling of P(NIPA-MA)/LPA semi-IPNs is strongly pH-dependent due to MA units incorporated into the copolymer network which already exhibits temperature-sensitivity by presence of PNIPA counterpart. Since the behavior of semi-IPNs is a combination of PMA, LPA, and PNIPA moieties, the sensitivity of swelling to external pH can be modified with increasing swelling temperature. At high pH conditions, LPA-doped semi-IPNs show elasticity representing soft and loosely cross-linked structure. Elastic modulus is higher in acidic pH condition due to the less swelling tendency, while in basic pH, the modulus decreases significantly in coordination with swelling. Oscillatory swelling reveals how fast semi-IPNs can respond to environmental pH change (2.1-10.7). By describing adsorption potential of semi-IPNs for cationic methylene blue uptake by pseudo-first-order and Freundlich model, the designed poly(NIPA-MA)/LPA semi-IPNs emerge as promising smart materials in applications requiring rapid response to changes in temperature and pH via diffusional properties.

Live-Cell Imaging of miRNAs with the Combination of CHA and HCR Techniques.

The abnormal expression of miRNA-21 is closely related to many cancers, and its sensitive detection plays an important role in the diagnosis and treatment of cancers. In the report, we designed a non-enzymatic amplification sensing system based on the catalytic hairpin assembly (CHA) and palindrome-based hybridization chain reaction (PHCR) technique for the detection and imaging of miRNA in living cells. Based on PHCR technology, two ingeniously designed palindrome-contained fluorescently labeled hairpin probes are sequentially opened upon the stimulation of short oligonucleotide triggers, promoting the autonomous assembly of cross-linked network-like structures (CNSs) and generating fluorescence resonance energy transfer (FRET) signal. Moreover, the PHCR technique can be combined with CHA technology to sufficiently improve amplification efficiency and signal output. By utilizing the CHA-PHCR sensing system, one miRNA-21 activates many triggers through CHA process and in turn initiates the assembly of CNSs by PHCR reaction, efficiently amplifying the FRET signal output. As such, the sensing system can detect target miRNAs down to 10pm with high detection specificity. Moreover, the CNS exhibits the enhanced intracellular stability, enabling the living cell imaging of miRNA-21. The CHA-PHCR sensing system can also screen the expression level of miRNA-21 in different living cells and differentiate cancer cells from healthy cells, which is consistent with the gold-standard PCR method.

Polyvinyl Butyral Solid Electrolyte Film and Its Electrochromic Laminated Safety Glass.

In recent years, the application of electrochromic laminated safety glass has attracted more and more attention, relying on polyvinyl butyral (PVB) solid electrolyte film. Herein, the ionic conductivity (σ) of the PVB film has been improved by a cross-linked structure and blended with LiClO4, which can reach as high as 1.78 × 10-4 S cm-1 at room temperature. In addition, their excellent comprehensive characteristics have been confirmed, such as mechanical strength, high visible light transmittance (>90%), high bond strength (4.2 MPa), and excellent thermal stability. Based on the PVB film above, WO3-laminated electrochromic devices with 5 × 5 cm2 and 10 × 10 cm2 areas are constructed. They can remain stable after 20 000 cycles monitored by cyclic voltammetry curves, indicating the PVB solid polymer electrolyte (PSPE) with a cross-linked structure has the potential commercial viability of large-area electrochromic devices (ECDs).

Synergistic Regulation of DNA Morphology by Metal Cations and Low pH.

As a flexible biomolecule, the spatial structure of DNA is variable. The effects of concentration, metal cations, and low pH on DNA morphology were studied. For the high concentration of DNA, the cross-linked branch-like or network structures were formed. For the low concentration of DNA, isolated, random and freely loose linear DNA chains were presented. These phenomena were related to the intermolecular interactions. Branch-like DNA structures were reformed with the addition of metal cations to the low concentration of DNA at pH 7-4, suggesting the negative charges of DNA were neutralized, thus transforming the spatial structure of DNA into a low charge density morphology and presenting the hypochromic effect. Compared to the monovalent alkaline metal cations, more negative charges of DNA were screened by the alkaline-earth metal cations. Distinct DNA morphologies were observed for pH 3. The linear and condensed DNA structures were simultaneously observed, which was met regardless of the solution with or without the addition of metal cations. This was further confirmed by the absorbance of DNA. Compared to the pure DNA, bulky and aggregated DNA collapsed structures were formed when the sodium and magnesium cations were added to the reaction solution. In addition, it was verified that the condensed DNA structures failed to revert back to the chain structure by neutralizing acidic solutions with alkali, but the compacted DNA spheres became loose. The conductivities of various DNA morphologies were measured. They were morphology-dependent. This study provides guidance forthe behavior of DNA in the acidic solutions and further promotes the application of DNA in DNA-based nano-optoelectronic devices.