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•A hybrid hydrogel with chemical and physical crosslinking exhibited excellent mechanical behaviors.•The hydrogel can be inflated into a big balloon and the membrane can quickly ...restore to its original state.•The relationship between chemical and physical crosslinking points in the various deformation stages of hydrogel.
Hybrid crosslinking hydrogels have exhibited excellent mechanical properties, however, the relationship between chemical and physical crosslinking in the various deformation stages is still indistinct. Here, a hybrid hydrogel was explored by inducing low density of chemical crosslinking into latex particle hydrogels (LP-Gel), in which latex particles act as physical crosslinking centers for inducing efficient aggregation of hydrophobic chains. The resulting hybrid hydrogel exhibited extraordinary mechanical performance. It is found that the role of chemical and physical crosslinking was different during different deformation levels. The synergistic effects of chemical and physical crosslinking allow hydrogels to dissipate a large number of energy, significantly enhancing the mechanical strength of hydrogels. Moreover, the hybrid hydrogel exhibited puncture resistant, excellent ductility and rapid recovery.
Pure tetragonal phase Ba sub(0.96)Sr sub(0.04)Zr sub(0.04)Y sub(0.005)Ti sub(0.955)O sub(2.9975) nano-powders were synthesized via a simple, fast and low cost method: polyacrylamide gel (PAG) method. ...The effects of processing parameters on the polymerization reaction and the sizes of as-prepared powder were investigated. The results reveal that the critical value of monomer / cross-linking agent ratio is 4.5:1 for the tightest network structure and the smallest average particle size of nano-powder correspondingly due to the smallest grid of gel. The monomer/cross-linking agent ratio and the concentration of cross-linking agent have significant influence on the gel quality and particle. In the investigation range we have probed into, the nano-dispersed BSZYT powders is obtained. The average native grain size of as-prepared powder is similar to 27 and similar to 45 nm after calcined at 900 degree C and 1200 degree C, respectively.
Most photocrosslinkable hydrogels have inadequacy in either mechanical performance or biodegradability. This issue is addressed by adopting a novel hydrogel design by introducing two different ...chitosan chains (catechol‐modified methacryloyl chitosan, CMC; methacryloyl chitosan, MC) via the simultaneous crosslinking of carbon–carbon double bonds and catechol‐Fe3+ chelation. This leads to an interpenetrating network of two chitosan chains with high crosslinking‐network density, which enhances mechanical performance including high compressive modulus and high ductility. The chitosan polymers not only endow the hydrogels with good biodegradability and biocompatibility, they also offer intrinsic antibacterial capability. The quinone groups formed by Fe3+ oxidation and protonated amino groups of chitosan polymer further enhance antibacterial property of the hydrogels. Serving as one of the two types of crosslinking mechanisms, the catechol‐Fe3+ chelation can covalently link with amino, thiol, and imidazole groups, which substantially enhance the hydrogel's adhesion to biological tissues. The hydrogel's adhesion to porcine skin shows a lap shear strength of 18.1 kPa, which is 6‐time that of the clinically established Fibrin Glue's adhesion. The hydrogel also has a good hemostatic performance due to the superior tissue adhesion as demonstrated with a hemorrhaging liver model. Furthermore, the hydrogel can remarkably promote healing of bacteria‐infected wound.
A novel photocrosslinkable, injectable, and tough chitosan hydrogel demonstrating a remarkable improvement in tissue adhesion and antibacterial activity is fabricated via double crosslinking (blue light crosslinking and catechol‐Fe3+ chelation) and double network design, suggesting that it can be promising as wound dressing for cutaneous tissue repair, remodeling, and regeneration.
A new method to protect/deprotect vinyl groups via sulfoxide chemistry realizes a thermally latent vinyl crosslinking system.
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•Utilization of sulfoxide chemistry for vinyl ...protection.•Synthesis of sulfoxide-functionalized crosslinkable monomer.•Preparation of sulfoxide-functionalized polymers for latent crosslinking reaction.•A realization of thermally latent crosslinking system.
Radical crosslinking reactions utilizing vinyl functionality are widely used to fabricate polymeric networks for bulk and surface applications. Here, we report a thermally latent vinyl crosslinking of polymers involving sulfoxide chemistry for the first time. Polymers with sulfoxide-protected methacrylate moieties are prepared via free-radical polymerization. These moieties are deprotected by a thermal process and transformed into methacrylate functional groups. The crosslinking behaviors of the protected polymers are investigated using an oscillatory rheometer in the presence of a radical initiator. The behavior strongly depended on the formation of methacrylate species in polymer chains. The thermally latent crosslinking approach introduces a novel method for the stepwise and systematic construction of polymeric networks that can potentially be applied in dual-curing or patterning processes.
This study compared properties of hydrogel chitosan sorbents crosslinked with eight agents, including four ionic ones: sodium citrate, sodium tripolyphosphate, sulfosuccinic acid, and oxalic acid and ...four covalent ones: glutaraldehyde, epichlorohydrin, trimethylpropane triglycidyl ether, and ethylene glycol diglycidyl ether. The effect of crosslinking process conditions (pH, temperature) and dose of the crosslinking agent on chitosan sorbent stability during sorption and on the effectiveness of Reactive Black 5 dye sorption were examined. The optimal parameters of crosslinking ensuring sorbent stability in acidic solutions and high sorption capability were established for each crosslinking agent tested. The susceptibility of crosslinked sorbents to mechanical damages was analyzed as well.
The process of ionic crosslinking was the most effective at the pH value below which hydrogel chitosan sorbent began to dissolve (pH4). The crosslinking temperature ranging from 25 to 60°C had no effect upon sorbent stability. The higher temperature during ionic crosslinking, however, slightly decreased RB5 sorption effectiveness. The ionic crosslinking significantly decrease the susceptibility of chitosan hydrogels to mechanical damages. In the case of covalent crosslinking of chitosan hydrogel beads, the effect of process conditions (pH, temperature) on the properties of the crosslinked sorbent depended on the type of crosslinking agent. The sorbents crosslinked with covalent agents were usually harder but also more fragile, and therefore more susceptible to mechanical damages.
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•The process of ionic crosslinking of chitosan is the most effective at pH≈4.•The higher temperature during ionic crosslinking decreases RB5 sorption effectiveness.•Overdosage of some ionic cross-linking agents may reduce the stability of the sorbent.•The covalently-crosslinked sorbents are more susceptible to mechanical damages.
The synthesis of 9‐methylanthracenyl glycidyl ether (AnthGE) as a crosslinkable monomer that can be applied in anionic ring opening polymerization is reported. Diblock terpolymers of the composition ...methoxy‐poly(ethylene oxide)‐block‐poly(2‐ethylhexyl glycidyl ether‐co‐9‐methylanthracenyl glycidyl ether) (mPEO‐b‐P(EHGE‐co‐AnthGE) with 10 to 24 wt% of AnthGE are synthesized and characterized. Their micellization behavior, as well as their light‐induced core‐crosslinking via irradiation with UV light (λ = 365 nm) is studied. The results are compared with studies on the dimerization, and the dimer cleavage via irradiation with UV–C light (λ = 254 nm), of the same diblock terpolymer in organic solution, and the small‐molecule model compound 9‐methoxymethylanthracene. Differences in 1H NMR spectra of the crosslinked or dimerized compounds and reaction kinetics of the dimerization reactions under different conditions suggest possible side reactions for the case of the core‐crosslinking of micelles in aqueous solution. These side reactions limit the reversibility of the anthracene dimerization reaction in aqueous solutions, even if the anthracene molecule is encapsulated within the hydrophobic core of a polymeric micelle.
Polyether‐based amphiphilic diblock terpolymers containing anthracene units, which can be crosslinked via UV irradiation (λ = 365 nm), are prepared. This 4+4‐cycloaddition reaction is partially reversible by irradiation with UV‐C light (λ = 254 nm). Investigation of the dimerization and dimer cleavage process showes the strong dependency of the dimerization reaction on the chemical environment (organic solution vs. aqueous micelles).
Wound dressings play a crucial role in protecting injured tissues and promoting the healing process. Traditional fabrication of antibacterial wound dressings can be complex and may involve toxic ...components. In this study, we developed an innovative hydrogel film (AP:GE@OTA/Ag) composed of amidated pectin (AP), gelatin (GE), oxidized tannic acid (OTA) at varying concentrations, and in-situ reduced silver nanoparticles (AgNPs). FTIR and XRD analyses confirmed that crosslinking occurs via interactions between OTA quinone groups and free amino groups in AP and GE. TEM imaging demonstrated the well-dispersed AgNPs with an average particle size of 58.64 nm, while the TG measurements indicated the enhancement of the thermal stability compared to AP:GE films. The AP:GE@OTA/Ag films exhibited superior fluid uptake ability (90.96 % at 2 h), water retention capacity (91.69 % at 2 h), and water vapor transmission rate (1903.29 g/m2/day), alongside improved tensile strength (38 MPa). Additionally, these films showed excellent cytocompatibility and sustained potent antimicrobial activity against S. aureus and E. coli with low AgNPs loadings of 1.02 ± 0.13 μg/cm2. NIT-1 mouse insulinoma cells demonstrated robust proliferation when cultured with the prepared dressings. These films significantly accelerated wound repair in a skin excision model, indicating their potential clinical applications for wound healing.
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•A soy protein-based adhesive was synthesized via adding a tailor-made crosslinker.•The crosslinker with multiple epoxy groups was designed without solvent or catalyst.•The adhesives ...with superior bonding strength and water resistance was prepared.
The weak bonding strength and poor water resistance of soy protein-based adhesive have limited its application as a non-formaldehyde adhesive in wood manufacturing industry. In this work, a novel soy protein-based adhesive was prepared by introducing a tailor-made crosslinker with multiple epoxy groups and flexible long chains without any solvent or catalyst via a one-pot strategy. The multiple epoxy groups could react with the hydrophilic groups (hydroxyl and amino) on the soy protein molecules to construct densely crosslinking networks, which was proved by the sol–gel results. The crosslinking networks were beneficial to enhancing the bonding strength and water resistance of the adhesive. Consequently, the dry bonding strength and the wet bonding strength were increased from 1.11 MPa and 0.22 MPa to 2.79 MPa and 1.12 MPa, respectively, marking increments of 151% and 409% when compared to the pristine soy protein-based adhesive. The bonding strength was beyond the standard of type II plywood (≥0.7 MPa, GB/T17657 − 2013). Furthermore, the flexible long chains of the crosslinker was also conductive to improving the toughness of the adhesive. Therefore, this work may open a feasible way to produce non-formaldehyde adhesives with superior bonding strength and water resistance, and thus broadening the application of soy protein.
Halide perovskite films processed from solution at low‐temperature offer promising opportunities to make flexible solar cells. However, the brittleness of perovskite films is an issue for mechanical ...stability in flexible devices. Herein, photo‐crosslinked 6,6‐phenylC61‐butyric oxetane dendron ester (C‐PCBOD) is used to improve the mechanical stability of methylammonium lead iodide (MAPbI3) perovskite films. Also, it is demonstrated that C‐PCBOD passivates the grain boundaries, which reduces the formation of trap states and enhances the environmental stability of MAPbI3. Thus, MAPbI3 perovskite solar cells are prepared on solid and flexible substrates with record efficiencies of 20.4% and 18.1%, respectively, which are among the highest ever reported for MAPbI3 on both flexible and solid substrates. The result of this work provides a step improvement toward stable and efficient flexible perovskite solar cells.
Embracing perovskite grains in a soft fullerene network represents a new and scalable approach, to make perovskite mechanically stable and thus compatible with flexible substrates. The method is demonstrated to prepare flexible perovskite solar cells with the highest ever reported power conversion efficiency. The superior mechanical stability from device performance under working conditions is characterized in situ.
Photo- and chemical crosslinking of proteins have offered various avenues for studying protein structure and protein interactions with biomolecules. Conventional photoactivatable groups generally ...lack reaction selectivity toward amino acid residues. New photoactivatable groups reacting with selected residues have emerged recently, increasing crosslinking efficiency and facilitating crosslink identification. Traditional chemical crosslinking usually employs highly reactive functional groups, while recent advance has developed latent reactive groups with reactivity triggered by proximity, which reduce spurious crosslinks and improve biocompatibility. The employment of these residue selective chemical functional groups, activated by light or proximity, in small molecule crosslinkers and in genetically encoded unnatural amino acids is summarized. Together with new software development in identifying protein crosslinks, residue selective crosslinking has enhanced the research of elusive protein-protein interactions in vitro, in cell lysate, and in live cells. Residue selective crosslinking is expected to expand to other methods for the investigation of various protein–biomolecule interactions.
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