Crosslinking Conditions Research Articles

Fabrication and Enhanced Flexibility of Starch-Based Cross-Linked Films.

The development of sustainable materials has driven significant interest in starch as a renewable and biodegradable polymer. However, the inherent brittleness, hydrophilicity, and lack of thermoplasticity of native starch limit its application in material science. This study addresses the limitations of native starch by converting it to dialdehyde starch (DAS) and cross-linking with polyether diamines via imine bonds. The effects of Jeffamine molecular weights (D-2000, D-400, and D-230) and mole ratios on the mechanical, thermal, and structural properties of starch-based films were examined. The cross-linked DAS/Js films exhibited significant enhancements in flexibility and toughness. Specifically, DAS/J2000 at a 0.03 mol ratio achieved a tensile strength of 62.9 MPa. In comparison, DAS/J400 at a 0.5 mol ratio demonstrated 126.2% elongation at break, indicating the balance between cross-linking density and chain mobility. X-ray diffraction (XRD) analysis revealed reduced crystallinity and tighter molecular packing with increased cross-linking. Dynamic mechanical analysis (DMA) indicated a decrease in Tg with an increasing mole ratio, reflecting enhanced molecular mobility. The results underscore the potential of optimized cross-linking conditions to produce starch-based films with properties that contribute to developing sustainable biopolymer materials.

Flame retardant epoxy vitrimers employing a Meldrum's acid-functionalized and phosphorus-containing bisphenol compound as the cross-linking agent for conventional epoxy

In addition to recycling and reprocessing features, designs of vitrimers possessing critical properties required for conventional cross-linked polymers are of interest. In this work, a newly designed Meldrum's acid (MA)-functionalized and phosphorus-containing bisphenol compound (P-MADV) compound is synthesized. Employing P-MADV as a curing agent, simultaneous formation of permanent and dynamic covalent linkages through one-pot reaction has been achieved in formation of flame retardant epoxy resin vitrimers. The newly synthesized P-MADV compound is an effective cross-linking agent for commercially-available epoxy resins for synthesis of flame-retardant epoxy vitrimers through the conventional cross-linking conditions and processes. The cross-linked epoxy vitrimer passes the flame test under UL 94V-0 specification contributed from the phosphorus-containing groups. The flame retardant vitrimer also exhibits a storage modulus of 1.2 GPa at 50 °C and a Tg (tanδ peak) of 185 °C, which are comparable to the values found with conventional phenolic novolac-cross-linked epoxy resin (storage modulus: 1.6 GPa; Tg: 155 °C). Without addition of catalysts for dynamic bond exchanging reaction, the cross-linked epoxy vitrimer shows stress relaxation time of 397 s at 230 °C and an activation energy of stress relaxation of 97.8 kJ mol−1. The dynamic features warrant the epoxy vitrimer being recyclable under thermally pressing at 230 °C and 16 MPa for 1 h. The recycled samples exhibit thermal and mechanical properties being comparable to the pristine resin. This work has demonstrated an attractive approach for preparation of flame retardant epoxy resin vitrimers in viewpoints of both manufacturing processes and resins properties.

Combining machine learning and molecular dynamics to predict strength-toughness and energy dissipation mechanisms of hybrid double-crosslinked CNT networks

Cross-linking has a significant strengthening effect on the mechanical properties of carbon nanoparticles, but there are still great challenges in how to control their mechanical properties through precise cross-linking ratios. Therefore, we use coarse-grained molecular dynamics (CGMD) to simulate its mechanical properties as data samples and combine it with machine learning methods to predict the optimal strength and toughness of carbon nanotubes (CNTs) corresponding to optimal cross-linking conditions. We found that the cross-linking density range is 2.60 ∼ 2.75 × 10-4/nm3, and the strong and weak cross-linking ratio range is 91 % S+9% W∼95 % S+5% W, which is the optimal range to achieve the mechanical properties of CNTs. Excessively high cross-link density and strong bond ratios can reduce the total number of cross-link bond breaks, thus decreasing their toughness. Meanwhile, high cross-linking density has a greater impact on the shear and slip between CNTs, tending to make CNTs brittle. Our proposed new approach for extracting data from coarse-grained models can obtain substantial optimization results without requiring much simulation computation. Furthermore, these cross-linking strategies and machine learning algorithms proposed in this work can provide a theoretical basis for controlling the mechanical properties of CNT materials, and also open up a new way for functional network materials other than CNTs.

Exploring the Role of Fibrin Gels in Enhancing Cell Migration for Vasculature Formation.

A hallmark of angiogenesis is the sprouting of endothelial cells. To replicate this event in vitro, biomaterial approaches can play an essential role in promoting cell migration. To study the capacity of a scaffold of fibrin (fibrinogen:thrombin mix) to support the movement of the endothelial cells, the migration area of spheroids formed with the HULEC cell line was measured. The cells were first allowed to form a spheroid using the hanging drop technique before being encapsulated in the fibrin gel. The cells' migration area was then measured after two days of embedding in the fibrin gel. Various conditions affecting fibrin gel polymerization, such as different concentrations of fibrinogen and thrombin, were evaluated alongside rheology, porosity, and fiber thickness analysis to understand how these factors influenced cell behavior within the composite biomaterial. Data point toward thrombin's role in governing fibrin gel polymerization; higher concentrations result in less rigid gels (loss tangent between 0.07 and 0.034) and increased cell migration (maximum concentration tested: 5 U/mL). The herein presented method allows for a more precise determination of the crosslinking conditions of fibrin gel that can be used to stimulate angiogenic sprouting.

Blood Coagulation Activities and Influence on DNA Condition of Alginate-Calcium Composites Prepared by Freeze-Drying Technique.

The aim of this research was to synthesize and characterize alginate-calcium composites using a freeze-drying method, with a focus on their potential applications in biomedicine. This study specifically explored the biochemical properties of these composites, emphasizing their role in blood coagulation and their capacity to interact with DNA. Additionally, the research aimed to assess how the cross-linking process influences the structural and chemical characteristics of the composites. Detailed analyses, including microscopic examination, surface area assessment, and atomic absorption spectrometry, yielded significant results. The objective of this study was to examine the impact of calcium chloride concentration on the calcium content in alginate composites. Specifically, the study assessed how varying concentrations of the cross-linking solution (ranging from 0.5% to 2%) influence the calcium ion saturation within the composites. This investigation is essential for understanding the physicochemical properties of the materials, including calcium content, porosity, and specific surface area. The results are intended to identify the optimal cross-linking conditions that maximize calcium enrichment efficiency while preserving the material's structural integrity. The study found that higher calcium chloride concentrations in alginate cross-linking improve the formation of a porous structure, enhanced by two-stage freeze-drying. Increased calcium levels led to a larger surface area and pore volume, and significantly higher calcium content. Furthermore, assays of activated partial thromboplastin time (aPTT) showed a reduction in clotting time for alginate composites containing calcium ions, indicating their potential as hemostatic agents. The aPTT test showed shorter clotting times with higher calcium ion concentrations, without enhanced activation of the extrinsic clotting pathway. The developed alginate material with calcium effectively supports hemostasis and reduces the risk of infection. The study also explored the capacity of these composites to interact with and modify the structure of plasmid DNA, underscoring their potential for future biomedical applications.

Fabrication and performance optimization of an advanced pervaporation desalination membrane: A study utilizing PVDF and hydrophilic active layer as composite

Pervaporation emerges as a promising technique for brine treatment. In this investigation, we employed a PVDF substrate layer and applied various coating solutions using a simple spray technique to produce a composite pervaporation membrane. The composite membrane's chemical structure, morphology, hydrophilicity, swelling property, surface roughness, and crosslinking conditions were thoroughly investigated. Notably, the PVDF/PEI/P(SS-MA) composite membrane exhibited outstanding desalination performance, demonstrating high salt rejection and flux of 308.7 ± 13.8 kg m−2 h−1 when subjected to a 3.5 wt% sodium chloride solution. Even at an elevated brine concentration of 20 wt%, the membrane maintained a commendable flux of 88.76 ± 5.4 kg m−2 h−1 at 72 °C. These findings underscore the efficacy of the developed composite membrane for brine desalination applications.

Light Switchable Bioorthogonal Reaction Manifold for Modulation of Hydrogel Properties.

Chemical reaction systems that can occur via multiple pathways in a controllable fashion are highly attractive for advanced materials applications and biological research. In this report, we introduce a bioorthogonal reaction manifold based on a chalcone pyrene (CPyr) moiety that can undergo either red-shifted photoreversible [2 + 2] cycloaddition or thiol-Michael addition click reaction. By coupling the CPyr to a water-soluble poly(ethylene glycol) end group, we demonstrate the efficient polymer dimerization and cleavage by blue light (λ = 450 nm) and UV light (λ = 340 nm), respectively. In the absence of light, CPyr rapidly reacts with thiols in aqueous environments, enabling fast and efficient polymer end-group functionalization. The chemical reaction manifold was further employed in polymer cross-linking for the preparation of hydrogels whose stiffness and morphology can be modulated by different photonic fields or the addition of a thiol cross-linker. The photoreversible cycloaddition and thiol-Michael addition click reaction can be used in conjunction for spatial and temporal conjugation of a streptavidin protein. Both cross-linking conditions are nontoxic to various cell lines, highlighting their potential in biomaterials applications.

Tuning Mechanical Properties, Swelling, and Enzymatic Degradation of Chitosan Cryogels Using Diglycidyl Ethers of Glycols with Different Chain Length as Cross-Linkers.

Cross-linking chitosan at room and subzero temperature using a series of diglycidyl ethers of glycols (DEs)-ethylene glycol (EGDE), 1,4-butanediol (BDDE), and poly(ethylene glycol) (PEGDE) has been investigated to demonstrate that DEs can be a more powerful alternative to glutaraldehyde (GA) for fabrication of biocompatible chitosan cryogels with tunable properties. Gelation of chitosan with DEs was significantly slower than with GA, allowing formation of cryogels with larger pores and higher permeability, more suitable for flow-through applications and cell culturing. Increased hydration of the cross-links with increased DE chain length weakened intermolecular hydrogen bonding in chitosan and improved cryogel elasticity. At high cross-linking ratios (DE:chitosan 1:4), the toughness and compressive strength of the cryogels decreased in the order EGDE > BDDE > PEGDE. By varying the DE chain length and concentration, permeable chitosan cryogels with elasticity moduli from 10.4 ± 0.8 to 41 ± 3 kPa, toughness from 2.68 ± 0.5 to 8.3 ± 0.1 kJ/m3, and compressive strength at 75% strain from 11 ± 2 to 33 ± 4 kPa were fabricated. Susceptibility of cryogels to enzymatic hydrolysis was identified as the parameter most sensitive to cross-linking conditions. Weight loss of cryogels increased with increased DE chain length, and degradation rate of PEGDE-cross-linked chitosan decreased 612-fold, when the cross-linker concentration increased 20-fold.

3D bioprinted mesenchymal stem cell laden scaffold enhances subcutaneous vascularization for delivery of cell therapy

Subcutaneous delivery of cell therapy is an appealing minimally-invasive strategy for the treatment of various diseases. However, the subdermal site is poorly vascularized making it inadequate for supporting engraftment, viability, and function of exogenous cells. In this study, we developed a 3D bioprinted scaffold composed of alginate/gelatin (Alg/Gel) embedded with mesenchymal stem cells (MSCs) to enhance vascularization and tissue ingrowth in a subcutaneous microenvironment. We identified bio-ink crosslinking conditions that optimally recapitulated the mechanical properties of subcutaneous tissue. We achieved controlled degradation of the Alg/Gel scaffold synchronous with host tissue ingrowth and remodeling. Further, in a rat model, the Alg/Gel scaffold was superior to MSC-embedded Pluronic hydrogel in supporting tissue development and vascularization of a subcutaneous site. While the scaffold alone promoted vascular tissue formation, the inclusion of MSCs in the bio-ink further enhanced angiogenesis. Our findings highlight the use of simple cell-laden degradable bioprinted structures to generate a supportive microenvironment for cell delivery.Graphical

Poly(glycerol sebacate)-based soft-tissue-mimicked active layers for triboelectric nanogenerators

Herein poly(glycerol sebacate) (PGS) has been synthesized and characterized to identify it’s potential as an active triboelectric layer in implantable and biodegradable TENG devices. The implantable and biodegradable TENG devices require excellent triboelectric properties, as well as the ability to mimic the mechanical properties of the surrounding tissues and exhibiting low cytotoxicity and eventual degradation and removal by bio-absorption. Two-step synthesis of PGS was carried out by using polycondensation between glycerol and sebacic acid in 1:1 molar ratio, followed by film preparation by spray-coating of the prepolymer solution. Crosslinking conditions were elaborated to yield good triboelectric performance together with low cytotoxicity. Triboelectric surface charge density of up to 0.188 nC cm−2 was obtained, exceeding the values of common triboelectric materials such as PDMS and PTFE by 2.89 and 3.76 times, respectively, when tested under identical contact-separation parameters. The mechanical properties of PGS can be tuned by varying the crosslinking degree to mimic soft tissues. In this context, in vitro studies on human skin fibroblasts revealed cell viability up to 78%. Furthermore, the cell viability is found to be strongly related to the crosslinking time of the PGS. The results show significantly lower cytotoxicity as compared to, for example, poly(sorbitol sebacate) and poly(hexanediol-co-citric acid). The flexibility and the confirmed biocompatibility beside the unique mechanical and physio-chemical collective properties of the of the polymer demonstrates the potential use of PGS for the next generation of implantable TENG devices.Graphical abstract

Stabilization of structure and channel height of two-dimensional montmorillonite membrane for efficient ion separation

As a new type of separation material, two-dimensional membrane has attracted wide attention due to its special transport mechanism. However, due to the hydration swelling of montmorillonite nanosheets, there are still challenges in preparing two-dimensional membrane with stable channel structure and fixed interlayer spacing. In order to overcome the problems caused by swelling, this study used polyvinyl alcohol and polyacrylic acid to stabilize the channel structure of two-dimensional membranes. Moreover, the crosslinking between Fe3+ and montmorillonite nanosheets was proposed to fix the interlayer spacing of two-dimensional membrane. It is found that various polymers had different effects on the mechanical property of two-dimensional membrane. The addition of polyvinyl alcohol and polyacrylic acid can significantly improve the tensile strength of the membrane. And the introduction of them reduces the hydrophilicity of the membrane surface, thus improving the stability of the membrane in water. In addition, the interlayer cations affect the stability of interlayer spacing of the membrane in water. After crosslinking the membrane with Fe3+, the interlayer spacing is fixed and can be maintained at about 0.94 nm in water for a long time. When a certain dosage of polyvinyl alcohol and PAA are added into the membrane and the crosslinking conditions are suitable, two-dimensional membrane has good selectivity to Li+ and Mg2+ in high Mg/Li ratio brine. Inspired by the natural ion exchange properties of montmorillonite, this study found a new method for inhibiting the hydration swelling of two-dimensional membrane and realizing precise control of interlayer spacing.

A novel sponge composite of chitosan-sodium tripolyphosphate-melamine for anionic dye Orange II removal

Since the potential carcinogenic, toxic and non-degradable dyes trigger serious environmental contamination by improper treatment, developing novel adsorbents remains a major challenge. A novel high efficiency and biopolymer-based environmental-friendly adsorbent, chitosan‑sodium tripolyphosphate-melamine sponge (CTS-STPP-MS) composite, was prepared for Orange II removing with chitosan as raw material, sodium tripolyphosphate as cross-linking agent. The composite was carefully characterized by SEM, EDS, FT-IR and XPS. The influence of crosslinking conditions, dosage, pH, initial concentration, contacting time and temperature on adsorption were tested through batch adsorption experiments. CTS-STPP-MS adsorption process was exothermic, spontaneous and agreed with Sips isotherm model accompanying the maximum adsorption capacity as 948 mg∙g−1 (pH = 3). Notably, the adsorption performance was outstanding for high concentration solutions, with a removal rate of 97 % in up to 2000 mg∙L−1 OII solution (100 mg sorbent dosage, 50 mL OII solution, pH = 3, 289.15 K). In addition, the adsorption efficiency yet remained 97.85 % after 5 repeated adsorption-desorption cycles. The driving force of adsorption was attributed to electrostatic attraction and hydrogen bonds which was proved by adsorption results coupled with XPS. Owing to the excellent properties of high-effective, environmental-friendly, easy to separate and regenerable, CTS-STPP-MS composite turned out to be a promising adsorbent in contamination treatment.

The Influence of Various Crosslinking Conditions of EDC/NHS on the Properties of Fish Collagen Film.

The process of crosslinking improves the physicochemical properties of biopolymer-based composites, making them valuable for biomedical applications. EDC/NHS-crosslinked collagen materials have a significant potential for tissue engineering applications, due to their enhanced properties and biocompatibility. Chemical crosslinking of samples can be carried out in several ways, which is crucial and has a direct effect on the final properties of the obtained material. In this study, the effect of crosslinking conditions on the properties of collagen films using EDC and NHS was investigated. Studies included FTIR spectroscopy, AFM, swelling and degradation tests, mechanical testing and contact angle measurements. Evaluation of prepared collagen films indicated that both crosslinking agents and crosslinking conditions influenced film properties. Notable alternations were observed in the infrared spectrum of the sample, to which EDC was added directly to the fish collagen solution. The same sample indicated the lowest Young modulus, tensile strength and breaking force parameters and the highest elongation at break. All samples reached the maximum swelling degree two hours after immersion in PBS solution; however, the immersion-crosslinked samples exhibited a significantly lower degree of swelling and were highly durable. The highest roughness was observed for the collagen film crosslinked with EDC, whereas the lowest was observed for the specimen crosslinked with EDC with NHS addition. The crosslinking agents increased the surface roughness of the collagen film, except for the sample modified with the addition of EDC and NHS mixture. All films were characterized by hydrophilic character. The films' modification resulted in a decrease in their hydrophilicity and wettability. Our research allows for a comparison of proposed EDC/NHS crosslinking conditions and their influence on the physicochemical properties of fish collagen thin films. EDC and NHS are promising crosslinking agents for the modification of fish collagen used in biomedical applications.

Precision Engineering of Chondrocyte Microenvironments: Investigating the Optimal Reaction Conditions for Type B Gelatin Methacrylate Hydrogel Matrix for TC28a2 Cells.

Gelatin methacrylate (GelMA) is a photocrosslinkable biomaterial that has gained widespread use in tissue engineering due to its favorable biological attributes and customizable physical and mechanical traits. While GelMA is compatible with various cell types, distinct cellular responses are observed within GelMA hydrogels. As such, tailoring hydrogels for specific applications has become imperative. Thus, our objective was to develop GelMA hydrogels tailored to enhance cell viability specifically for TC28a2 chondrocytes in a three-dimensional (3D) cell culture setting. We investigated GelMA synthesis using PBS and 0.25M CB buffer, analyzed the mechanical and physical traits of GelMA hydrogels, and evaluated how varying GelMA crosslinking conditions (GelMA concentration, photoinitiator concentration, and UV exposure time) affected the viability of TC28a2 chondrocytes. The results revealed that GelMA synthesis using 0.25M CB buffer led to a greater degree of methacrylation compared to PBS buffer, and the LAP photoinitiator demonstrated superior efficacy for GelMA gelation compared to Irgacure 2959. Additionally, the stiffness, porosity, and swelling degree of GelMA hydrogels were predominantly affected by GelMA concentration, while cell viability was impacted by all crosslinking conditions, decreasing notably with increasing GelMA concentration, photoinitiator concentration, and UV exposure time. This study facilitated the optimization of crosslinking conditions to enhance cell viability within GelMA hydrogels, a critical aspect for diverse biomedical applications.

Plasma-Induced Graft Polymerization for the In Situ Synthesis of Cross-Linked Nanocoatings.

Conventional technology for the modification of surfaces loaded with nanomaterials typically requires a three-step process: (1) the construction of a polymer platform, (2) the synthesis of nanoparticles (NPs), and (3) the immobilization or anchoring of NPs. During the immobilization or anchoring process, there is an unavoidable excess of NPs primarily situated at the top of the surface, resulting in the agglomeration of aggregates. These aggregates can form different shapes and sizes, often creating an uneven distribution of NPs, resulting in an unstable coating that gradually releases NPs over time. In this study, argon plasma technology was used to create an innovative nanocoating consisting of polymer chains that are cross-linked to metal NPs, forming a polymer composite. To do this, argon plasma was employed as both an oxidizing and reducing agent during different steps in the nanocoating fabrication process. More specifically, a "grafting-from" approach, coupled with in situ argon plasma-assisted reduction of Cu2+ to Cu0, provided an innovative means for the construction of the nanocoating. With this "grafting-from" approach, the covalent binding of acrylic acid monomers to a surface results in a negatively charged nanocoating when exposed to solutions of a pH greater than 4.5. Due to its negative charge, the nanocoating can bind cations from solution, creating a platform for the in situ argon plasma-assisted reduction of Cu2+ to primarily Cu0 NPs (CuNPs). By controlling grafting conditions, in situ plasma-assisted reduction of NPs, and cross-linking conditions, we can generate nanocoatings with specific (1) polymer graft density and film thickness, (2) NP concentration cross-linked to polymer chains, and (3) NP composition. Under optimal experimental conditions, a nonleaching cross-linkage occurs between the nanocoating and the NPs, with only minimal NP aggregation. We have used this technology to engineer cross-linked nanocoatings possessing extremely low amounts of CuNPs (4.02 μg/cm2), which are distributed within the nanocoating and are capable of preventing infections.

Open-system force-elongation relationship of collagen in chemo-mechanical equilibrium with water

A significant deformation mechanism of collagen at low loads is molecular uncoiling and rearrangement. Although the effect of hydration and cross-linking has been investigated at larger loads when collagen undergoes molecular sliding, their effects on collagen molecular reorganization remain unclear. Here we develop two thermodynamic models that use the notion of open-system elasticity to elucidate the effect of swelling due to water uptake during deformation of collagen networks under low and high cross-linking conditions. With low crosslinking, entropic contributions dominate resulting in rejection of solvent from the polymer network leading to reduced collagen stiffness with increased loads. Contrarily, high cross-linking inhibits initial coiling and structural kinking and the mechanical behavior is dominated by elastic energy. In this configuration, the solvent content depends on the sign of the applied load resulting in a non-linear open-system stress-strain relationship. The models provide insight on the parameters that impact the stress-strain relationships of hydrated collagen and can inform the way collagenous matrices are treated both in medical and laboratory settings.

Controlled delivery of 5-fluorouracil from monodisperse chitosan microspheres prepared by emulsion crosslinking.

This work aims to determine the optimal conditions for emulsion cross-linking of chitosan (CHS) with various molecular weights using glutaraldehyde as a cross-linking agent to produce 5-fluorouracil-loaded CHS microspheres (5-FU/CHS). Their drug loading and encapsulation efficiencies are found to be in the range of 3.87-12.35% and 20.13-70.45%, respectively. The dynamic light scattering results show that 5-FU/CHS microspheres are micron-sized with a uniform size distribution, and the scanning electron microscopy results show that they are spherical. The results of thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy demonstrate that 5-FU is successfully incorporated into the microspheres. The in vitro release tests show that 5-FU/CHS have a prolonged, pH-responsive release pattern of 5-FU, and the cumulative release rate under acidic condition is much larger than that under neutral conditions. The drug release kinetic analysis further demonstrates that the release of 5-FU can be well described by the Fickian diffusion model.

(Invited) Binder Investigation for Silicon Electrode of Lithium-Ion Batteries

Though the binder is not an active material and does not contribute capacity to lithium ion batteries (LIBs), it is an important ingredient for maintaining the integrity of the electrode, which helps to improve electrical contact between the active materials and conductive carbon black, improves the Li+ transport efficiency, reduces the internal resistance of Li-ion batteries and effectively depresses the crack formations and phase separation.Polyvinylidene fluoride (PVDF) is a polymer that is commonly used as a binder for both anode and cathode materials in LIBs. However, it is not suitable for Si electrode due to its poor binding capability and stability. Viewed as a next generation anode material, Si has been extensively studied due to its extremely high theoretical specific capacity of 3578 mAh/g (assuming Li15Si4 as intermediate product). However, silicon undergoes huge volume variations during repeated discharge and charge, which requires a strong binder to maintain the electrode mechanical integrity. Developing a high strength binder for silicon anodes has been considered as an efficient pathway to alleviate various capacity decay pathways.Polyacrylic acid (PAA) and its lithiated version (LiPAA), rich with carboxy function group, can provide stronger binding and are widely used as binder for Si electrode. In this work, we optimized Si electrode formulation by varying the binder composition. The optimized Si electrodes were electrochemically tested in both half cells and full cells. With improvement in electrochemical performance, cracks at the electrode level can still be observed for the cycled electrodes, which suggests that a stronger binder is required to mitigate volume expansion of Si electrodes and hold the particles together.We further studied the polyimide (PI) materials as binders for Si anodes in an attempt to achieve more stable cycling performance. In this work, we explore various PI crosslinking conditions and their effects on electrochemical performance. The optimized silicon electrode exhibits a higher tensile strength than that of conventional PAA binder. The strong adhesion of the PI binder suppresses the structural collapse of the Si negative electrode during lithiation/delithiation, enabling good capacity retention and stable cycle life.

Development of a novel PPTA/cellulose composite insulation paper with low dielectric constant and improved mechanical properties by BTCA crosslinking

AbstractThis study investigates the effect of 1,2,3,4‐butane tetracarboxylic acid (BTCA) crosslinking treatment on the electrical properties of poly‐p‐phenylene terephthalate (PPTA)/cellulose insulation paper to prepare a novel composite insulation paper with low dielectric constant and good electrical performance. Three‐layer PPTA/cellulose composite paper crosslinked by BTCA under various conditions, composite paper without crosslinking, directly mixed composite paper, and conventional Kraft paper are prepared. The morphology and surface chemical composition of the paper samples are characterized. Dielectric, mechanical, and thermal properties are investigated. Results show that the BTCA concentration of 0.2 mol L−1 with a 180°C curing temperature is the relatively superior crosslinking condition to prepare a novel composite with low dielectric constant and good comprehensive performance. The dielectric constant and loss of the novel composite paper decrease to 3.21 and 0.392 at 50 Hz. The tensile strength of the BTCA crosslinked three‐layer PPTA/cellulose composite paper (thickness: 130 μm) has reached 10.01 kN m−1, increased by 41.6% than the directly mixed composite paper. The novel BTCA crosslinked composite paper also shows improved thermal stability. The BTCA crosslinking proves to be a promising method to improve the dielectric properties and electrical performance of the PPTA/cellulose composite paper.

Preparation of enzymatically cross-linked α-lactalbumin nanoparticles and their application for encapsulating lycopene.

High internal phase Pickering emulsions (HIPPEs) stabilized by protein nanoparticles have been widely reported, but the use of enzymatic methods for preparing these nanoparticles remains underexplored. Our hypothesis is that enzymatically crosslinked α-lactalbumin (ALA) nanoparticles (ALATGs) prepared using transglutaminase will demonstrate improved properties as stabilizers for HIPPEs. In this study, we investigated the physicochemical properties and microstructures of ALATGs, finding that enzymatic crosslinking could be enhanced by removing Ca2+ ions from ALA and preheating the proteins (85°C, 15min). The electrical charge, secondary structure, and surface hydrophobicity of ALATGs were found to depend on crosslinking conditions. HIPPEs formed with an ALA concentration of 10mg/mL and an enzyme activity of 120U/g exhibited the highest apparent viscosity and mechanical strength, as well as significantly improved loading capacity and photostability for the encapsulated lycopene. Overall, our results support the hypothesis that ALATG-nanoparticles show superior performance as emulsifiers compared to ALA-nanoparticles.