Cross-linked Systems Research Articles

In-situ crosslinked polyetherimide/BNNS composites with ultrahigh charged-discharged efficiency at high temperature

High performance dielectric polymer composites for capacitive energy storage have been a hot topic in recent years. However, dielectric materials tend to breakdown at high temperature, and its charged-discharged efficiency is greatly reduced. Therefore, preparing high-efficient high-temperature dielectric material is the main challenge in this field. In this work, based on the synergistic effect of in-situ composite and controlled thermal cross-linking, the thermal conducting nano filler and crosslinking system composite has ultra-high charged-discharged efficiency at high temperature. It is proved that the addition amount of BNNS for the peak performance of this kind of composite is 10 vol% and the discharge energy density is 4.58 J/cm3 and the charged-discharged efficiency reaches 96 % at 150 °C and 500 MV/m. At 200 °C and 300 MV/m, these are 1.76 J/cm3 and astonishing 95 %. It is expected to be a candidate for a new generation of high temperature resistant dielectric materials.

Flavin mononucleotide in visible light photoinitiating systems for multiple-photocrosslinking and photoencapsulation strategies

Visible light-induced photocrosslinking techniques have attracted significant attention for their flexibility, controllability, safety, and energy conservation, especially in tissue engineering and biofabrication, compared to UV photocrosslinking. Despite these advantages, current photoinitiators are constrained by various challenges, including inadequate photoinitiation efficiency, low biocompatibility, poor water solubility, and limited compatibility with diverse crosslinking systems. Here, a water-soluble derivative of riboflavin, flavin mononucleotide (FMN−), was used to assess its potential as an initiator in multiple-photocrosslinking systems, including radical photopolymerization, dityrosine, and ditryptophan coupling crosslinking, under blue light irradiation. Blue light irradiation facilitated an efficient electron transfer reaction between FMN− and persulfate, owing to their suitable spectral compatibility and photoactivity. The resulting oxidizing free radicals and excited triplet state of FMN− served as initiating active species for the multiple-photocrosslinking reactions. The combination of FMN− and potassium persulfate (KPS) exhibited exceptional photoinitiation efficiency for various biomaterials, including silk fibroin, gelatin, poly(ethylene glycol) diacrylate, and carboxymethyl cellulose modified with amino acids. Furthermore, the cytocompatibility of the FMN−/KPS photoinitiator was demonstrated by the survival rates of 3T3-LI fibroblasts encapsulated in it, which exceeded 95 % when compared to a commercial initiator. Statement of significanceBy introducing persulfate, the photoinitiation efficiency of flavin mononucleotide was significantly improved. The application scenarios of flavin mononucleotide and persulfate combinations were also greatly extended, including radical photopolymerization, dityrosine, diphenylalanine, and ditryptophan coupling crosslinking. Among them, the coupling crosslinking of amino acids (di-phenylalanine, and di-tryptophan) modified carboxymethyl cellulose, to our knowledge, was first reported. The excellent cytocompatibility of cell encapsulation further proved that the combinations of flavin mononucleotide and persulfate have great potential in tissue engineering.

Thermally stable 3D cross-linked fluorinated polyimide/PVDF-HFP hybrid separator for lithium battery applications

Commercial Celgard 2325 separators suffer from poor flexibility, poor electrolyte wettability, and thermal instability, which can cause internal short circuits and thermal runaway in lithium rechargeable batteries. A novel 3D cross-linked and thermotolerant fluorinated polyimide (PI) / PVDF-HFP (PV) hybrid nanofiber separator rich in polar functional groups was fabricated using an electrospinning technique. PI and PV polymers are joined by a hydrogen bond through their exposed amide (–NH) and fluorinated (-CF) functional groups to build a supramolecular polymer cross-linked system. The separator exhibited high porosity (75 %), outstanding electrolyte uptake ability (775 %), strong mechanical properties (15.7 MPa), excellent thermal stability, and flexibility. As a result, the separator showed excellent Li+-conductivity (3.3 mS cm−1) and high Li+-transference number (tLi+ = 0.7) and maintained a proper-contacted electrolyte/electrode interaction for stable Li plating/stripping. Furthermore, when the PI/PV hybrid separator was applied in anode-free Li-metal batteries (a protocol of Cu/NMC cell), or Li-ion (MCMB /NMC) batteries, the cells achieved a high capacity and long lifetime. Remarkably, the Cu/NMC cell fabricated with a PI/PV hybrid separator is more robust and continues to function even after being heated at a high temperature of 140 °C for 1 h.

The effect of cross-linking system and reinforcement on the cross-linking reaction of peroxide vulcanized ethylene-propylene-diene terpolymer (EPDM) matrix

In this work, the effect of using of dicumyl-peroxide (DCP) (2, 5 & 8 phr) and co-agent triallyl-cyanurate (TAC) (2, 4 & 6 phr) as cross-linking system as well as multi-walled carbon nanotubes (MWCNTs) (5, 8 και 10 phr) as a filler, for ethylene-propylene-diene terpolymer (EPDM) was investigated. Differential scanning calorimetry (DSC) was employed in order to study the progress of the cross-linking reaction, based on the exothermic vulcanization peaks of isothermal (at 160, 170, 180, 190 °C) and non-isothermal experiments (with heating rates 5, 10, 25, 50 °C min−1). The autocatalytic model was successfully applied to the results of isothermal experiments and the activation energy (Ea) of the reaction was calculated, based on the Arrhenius equation. The Ozawa-Kissinger equations were also applied to the data obtained from the non-isothermal study. From the results obtained from isothermal DSC experiments, an increase was observed in the reaction rates accompanied with a decrease in Ea with the increase of DCP content, whereas a proportional relationship between TAC content and the enthalpy and Ea of the reaction was recorded. The incorporation of MWCNT’s in EPDM increased its Ea. From the non-isothermal DSC experiments, a significant increase in the enthalpy and Ea of the cross-linking reaction was observed at higher DCP content, whereas TAC content did not show any notable effect on the reaction. Based on the results of this research, it is concluded that the increase of peroxide content facilitates the vulcanization of EPDM, whereas inhibition was observed by the incorporation of MWCNT’s.

Molded-In Foaming(MIF) 공정에 적합한 가교 시스템에 관한 연구

Molded-In Foaming(MIF) 공정에 적합한 가교 시스템에 관한 연구

Development and Bioactivity of Zinc Sulfate Cross-Linked Polysaccharide Delivery System of Dexamethasone Phosphate.

Improving the biopharmaceutical properties of glucocorticoids (increasing local bioavailability and reducing systemic toxicity) is an important challenge. The aim of this study was to develop a dexamethasone phosphate (DexP) delivery system based on hyaluronic acid (HA) and a water-soluble cationic chitosan derivative, diethylaminoethyl chitosan (DEAECS). The DexP delivery system was a polyelectrolyte complex (PEC) resulting from interpolymer interactions between the HA polyanion and the DEAECS polycation with simultaneous incorporation of zinc ions as a cross-linking agent into the complex. The developed PECs had a hydrodynamic diameter of 244 nm and a ζ-potential of +24.4 mV; the encapsulation efficiency and DexP content were 75.6% and 45.4 μg/mg, respectively. The designed DexP delivery systems were characterized by both excellent mucoadhesion and prolonged drug release (approximately 70% of DexP was released within 10 h). In vitro experiments showed that encapsulation of DexP in polysaccharide nanocarriers did not reduce its anti-inflammatory activity compared to free DexP.

Incorporation of Zr-based metal-organic polyhedron into the PDA/PVDF adsorptive membrane for rapid removal of Cr(VI)

Zirconium-based metal-organic polyhedra (ZrMOPs) have gained significant attention owing to their well-defined cavities, stability and potential applications. Herein, a novel composite membrane (PDA/ZrT-1-NH2/PVDF) was developed by incorporating amino-functionalized ZrMOP (ZrT-1-NH2) into polydopamine (PDA) and trimesoyl chloride (TMC) cross-linking system. Notably, the cationic ZrT-1-NH2 cages were immobilized onto the membrane surface by a simple vacuum filtration method, which thus endowed the surface positive charge for the membrane. A pre-prepared composite membrane was used to remove Cr(VI) from the wastewater. The effects of pH, contact time, initial Cr(VI) concentration, temperature, coexisting ions competition and reusability were investigated in batch experiments. The results revealed the as-prepared composite membrane exhibited high removal efficiency of 96.6 % for Cr(VI) ions within 5 min. In addition, the adsorption rate was very fast, reaching adsorption equilibrium in less than 30 min. Finally, a possible adsorption mechanism was proposed. The adsorption process was dominated by physical adsorption accompanied by a partial reduction of Cr(VI) to Cr(III).

Cytocompatibility Evaluation of PEG-Methylsulfone Hydrogels.

Methylsulfone derivatized poly(ethylene) glycol (PEG) macromers can be biofunctionalized with thiolated ligands and cross-linked with thiol-based cross-linkers to obtain bioactive PEG hydrogels for in situ cell encapsulation. Methylsulfonyl-thiol (MS-SH) reactions present several advantages for this purpose when compared to other thiol-based cross-linking systems. They proceed with adequate and tunable kinetics for encapsulation, they reach a high conversion degree with good selectivity, and they generate stable reaction products. Our previous work demonstrated the cytocompatibility of cross-linked PEG-MS/thiol hydrogels in contact with fibroblasts. However, the cytocompatibility of the in situ MS-SH cross-linking reaction itself, which generates methylsulfinic acid as byproduct at the cross-linked site, remains to be evaluated. These studies are necessary to evaluate the potential of these systems for in vivo applications. Here we perform an extensive cytocompatibility study of PEG hydrogels during in situ cross-linking by the methylsulfonyl-thiol reaction. We compare these results with maleimide-thiol cross-linked PEGs which are well established for cell culture and in vivo experiments and do not involve the release of a byproduct. We show that fibroblasts and endothelial cells remain viable after in situ polymerization of methylsulfonyl-thiol gels on the top of the cell layers. Cell viability seems better than after in situ cross-linking hydrogels with maleimide-thiol chemistry. The endothelial cell proinflammatory phenotype is low and similar to the one obtained by the maleimide-thiol reaction. Finally, no activation of monocytes is observed. All in all, these results demonstrate that the methylsulfonyl-thiol chemistry is cytocompatible and does not trigger high pro-inflammatory responses in endothelial cells and monocytes. These results make methylsulfonyl-thiol chemistries eligible for in vivo testing and eventually clinical application in the future.

Nanocomposite hydrogels: an optimistic insight towards the treatments of ocular disorders.

The distinct anatomy and physiology of the eye represent it as a specialized organ. The noumenal physiological barriers, whose prominent role is to prevent the entrance of extracellular substances, reduce the bioavailability of medicines taken locally. Nanocarriers offer many advantages, such as site-specific drug delivery, reduced dose-related side effects, more drug loading capacity, etc. Nanoparticles, nano micelles, Nanostructured Lipid Carriers (NLCs), Solid Lipid Nanoparticles (SLNs), liposomes, polymeric nanoparticles, microspheres, microemulsions, etc., have all undergone significant analysis to overcome numerous static and dynamic obstacles. Among the several methods of delivering drugs, one of the most captivating and demanding is ocular drug delivery (ODD). The intent of developing formulations for an extended period can be partially achieved via thermoresponsive hydrogels. It is feasible to store fluids inside a cross-linked gel system for efficient long-term administration owing to hydrogels, which are hydrophilic polymeric networks with excellent three-dimensional structures and water or biological fluid absorption capacities. Hydrogels can be incorporated into nanocarriers to achieve site-specific action and prolonged release. Related patents and research reports with various platforms like Science Direct, Springer, PubMed, Google Scholar, Shodhganga, and Patseer were used to gather the data, and a search methodology was availed. The paper thoroughly summarizes the strategies for incorporating drugs with hydrogel into a nanocarrier to provide sustained release and prolonged therapeutic effects. According to the comprehensive review of literature and patents like (US2015374633A1), (US10980882B2), and (WO2011018800A2), nanocarrier-loaded thermoresponsive hydrogels show promising results. Due to their propensity to alter state in reaction to temperature changes, thermoresponsive hydrogels can improve medication bioavailability. Intervening nanocarriers loaded hydrogels directly on the targeted site displays local intervention and site-specificity. Thus, the use of nanocarriers in ocular drug delivery is encouraging.

Thermal-driven cationic waterborne polyurethane crosslinker with oxime-based and catechol structure for the preparation of soybean protein-based adhesive with excellent adhesion properties

Recently, the research of waterborne polyurethane (WPU) as toughening matrix of soybean protein-based adhesives has attracted much attention. However, the intermolecular interaction between polyurethane and protein molecules is too weak to construct a compact crosslinking system to achieve strengthening and toughening adhesive systems. In this work, a thermal-driven cationic waterborne polyurethane (CWPOU) with oxime-isocyanate groups and catechol groups was synthesized. The obtained CWPOU emulsion was introduced into soybean meal (SM) matrix to fabricate a SM/CWPOU bio-adhesive. Thermal-driven elements in polyurethane molecules released isocyanate groups, increasing covalent crosslinking between crosslinker and protein molecules, synergies with non-covalent forces formed between catechol structures to improve the comprehensive bonding properties of the adhesives. As a result, the dry/wet bonding strengths of the modified adhesives were noticeably enhanced with the highest values observed (SM/CWPOU-4) reaching 169.6% and 191.4% that of pure SM adhesives, respectively. Furthermore, the hydrogen bonding provided by hard segments of polyurethane and noncovalent forces between catechol groups and wood substrates contributed to excellent cold-pressing performance of the bio-adhesives with a maximum value pleasantly reaching 298% that of pure SM. The mildew resistances of SM/CWPOU adhesives were attributed to bactericidal performance of the cationic structures and catechol groups in CWPOUs. This work provides an effective method to prepare the “green” and high-performance protein-based adhesives.

Cascade enzymatic preparation of carboxymethyl chitosan-based multifunctional hydrogels for promoting cutaneous wound healing

Designing wound dressings with inherent multifunctional therapeutic effects is desirable for clinical applications. Herein, a series of multifunctional carboxymethyl chitosan (CMCS)-based hydrogels were fabricated by the facile urate oxidase (UOX)-horseradish peroxidase (HRP) cascade enzymatic crosslinking system. For the first time, the cascade enzymatic crosslinking system was not only used for preparing hydrogel wound dressings but also for accelerating wound healing due to the activity retention of the self-compartmental enzymes. A CMCS derivative (HCMCS-mF) synthesized by successively grafting 4-hydroxybenzaldehyde (H) and 5-methylfurfural (mF) on CMCS and a quaternary ammonium crosslinker (QMal) with terminal grafting maleimide (Mal) groups were combined with enzymatic system for the facile preparation of hydrogels. The mild Diels-Alder (DA) crosslinking reaction between mF and Mal groups constructed the first network of hydrogels. The cascade UOX-HRP system mediated the oxidative crosslinking of phenols thus forming the second gel network. Self-entrapped UOX maintained its enzymatic activity and could continuously catalyze the oxidation of uric acid, generating therapeutic allantoin. These porous, degradable, mechanically stable hydrogels with excellent antioxidant performance and enhanced antibacterial capacity could effectively accelerate skin wound repair by simultaneously reducing oxidative stress, relieving inflammation, promoting collagen deposition and upregulating the expression level of CD31.

Preparation and laboratory study of a sodium carboxymethyl cellulose smart temperature‐controlled crosslinked gel fracturing fluid system

AbstractWater‐based fracturing fluids are widely used in the development of tight, low‐permeability unconventional oil and gas fields, where the crosslinking agent component can thicken the low‐viscosity, high‐flowability base fluid to ensure sufficient proppant is transported from the wellbore to the tip of the fracture and generate the required net pressure to support the fracture. Zirconium crosslinking agents are widely used due to their good stability and high shear resistance. In the paper, glycerin, zirconium chloride, lactic acid, sodium hydroxide, and water were reacted at a molar ratio of 7:1:3:4:98 and a temperature of 80°C for 5 h; Using triethanolamine, zirconium chloride, lactic acid, and water as raw materials, the molar ratio of 4:1:3:98, reaction at 80°C for 5 h, and then zirconium lactate crosslinker and triethanolamine zirconium lactate crosslinker were synthesized respectively, which were incorporated into a newly designed self‐generating acid temperature‐controlled crosslinking system to crosslink salt‐resistant cleaning fracturing fluids mainly composed of sodium carboxymethyl cellulose, achieving delayed crosslinking of the fracturing fluid in different temperature formations. The strong crosslinking temperature range of glycerol‐lactic acid zirconium and the rheological properties of triethanolamine zirconium lactate gel and zirconium lactate gel in the system were tested. The viscosity of triethanolamine zirconium lactate gel and zirconium lactate gel were 88.86 and 94.69 mPa·s, respectively, at the shear rate of 300 s−1, and the viscosity remained above 200 mPa·s at the shear rate of 170 s−1, 60°C for 1 h. These figures far exceed the gels formed by commercially purchased zirconate. This system can make glycerol lactic achouid zirconium crosslinking agents undergo strong crosslinking at 40–65°C and triethanolamine lactic acid zirconium undergo strong crosslinking at 55–75°C. It has significant implications for the delayed crosslinking effect of massive fracturing operations.

A self-healing hydrogel and injectable cryogel of gelatin methacryloyl-polyurethane double network for 3D printing.

Three-dimensional (3D) printing of soft biomaterials facilitates the progress of personalized medicine. The development for different forms of 3D-printable biomaterials can promotes the potential manufacturing for artificial organs and provides biomaterials with the required properties. In this study, gelatin methacryloyl (GelMA) and dialdehyde-functionalized polyurethane (DFPU) were combined to create a double crosslinking system and develop 3D-printable GelMA-PU biodegradable hydrogel and cryogel. The GelMA-PU system demonstrates a combination of self-healing ability and 3D printability and provides two distinct forms of 3D-printable biomaterials with smart functions, high printing resolution, and biocompatibility. The hydrogel was printed into individual modules through an 80µm or larger nozzle and further assembled into complex structures through adhesive and self-healing abilities, which could be stabilized by secondary photocrosslinking. The 3D-printed hydrogel was adhesive, light transmittable, and could embed a light emitting diode (LED). Furthermore, the hydrogel laden with human mesenchymal stem cells (hMSCs) was successfully printed and showed cell proliferation. Meanwhile, 3D-printed cryogel was achieved by printing on a subzero temperature platform through a 210µm nozzle. After secondary photocrosslinking and drying, the cryogel was deliverable through a 16-gage (1194µm) syringe needle and can promote the proliferation of hMSCs. The GelMA-PU system extends the ink pool for 3D printing of biomaterials and has potential applications in tissue engineering scaffolds, minimally invasive surgery devices, and electronic wound dressings. STATEMENT OF SIGNIFICANCE: The 3D-printable biomaterials developed in this work are GelMA-based ink with smart funcitons and have potentials for various customized medical applications. The synthesized GelMA-polyurethane double network hydrogel can be 3D-printed into individual modules (e.g., 11×11×5mm3) through an 80μm or larger size nozzle, which are then assembled into a taller structure over five times of the initial height by self-healing and secondary photocrosslinking. The hydrogel is adhesive, light transmittable, and biocompatible that can either carry human mesenchymal stem cells (hMSCs) as bioink or embed a red light LED (620nm) with potential applications in electronic skin dressing. Meanwhile, the 3D-printed highly compressible cryogel (e.g., 6×6×1mm3) is deliverable by a 16-gage (1194μm) syringe needle and supports the proliferation of hMSCs also.

Isocyanate-free Carboxyl-terminated Polybutadiene and Epoxidised Hydroxyl-terminated Polybutadiene Cross-linking System as a Binder in Solid Heterogeneous Propellants

Isocyanate-free Carboxyl-terminated Polybutadiene and Epoxidised Hydroxyl-terminated Polybutadiene Cross-linking System as a Binder in Solid Heterogeneous Propellants

High-flux loose nanofiltration membrane with anti-dye fouling ability based on TA@ZIF-8 for efficient dye/salt separation

Herein, we report a preparation method based on a modified zeolite imidazolate skeleton loose nanofiltration membrane used to achieve the efficient separation of salt and dye from dye wastewater. In this study, negatively charged hydrophilic TA@ZIF-8 was synthesized using a tannin surface-functionalization-assisted etching process by tannic acid (TA). A novel, highly negatively charged, and loose nanofiltration membrane was then prepared by adding TA@ZIF-8 to a polyethyleneimine (PEI) and tricarboxylic acid (TMA) crosslinking system. The addition of TA@ZIF-8 nanoparticles not only changed the degree of crosslinking of PEI/TMA but also provided a preferential channel for water molecules, thereby improving the flux of the membrane. Then, the success of TA@ZIF-8 NPs and membranes preparation were verified by SEM, XRD, FT-IR, TGA, BET, XPS and other methods. The results showed that the optimal preparation conditions were 0.020 wt% TA@ZIF-8 loading, and the contact angle of the membranes decreased from 79.8° to 53.7°. The water flux of the membrane is 81 L·m−2·h−1·bar−1, which is 1.5 times that of PEI/TMA membrane. In addition, TA@ZIF-8–2 membrane not only has high rejection rate for Methyl blue (98.7 %), Toluidine blue (89.6 %), Cr6+ (91.2 %), but also maintains high transmittance for NaCl and Na2SO4. Besides, the separation performance of the membrane was stable for a long time in a mixed solution of dye and salt and excellent antifouling performance. Therefore, the loose TA@ZIF-8/PEI/TMA nanofiltration membrane has broad application prospects in printing and dyeing wastewater treatments.

Effect of the Chemical Modification of Diatomite/Isotactic Polypropylene Composite on the Rheological, Morphological and Mechanical Properties

The present study deals with the effect of the Diatomite (D) microcomposite with and without chemical modification in a polypropylene (iPP) blend. The objective is to achieve a material with a better performance at a lower cost and more accessible and more suitable processing. The chemical surface modification of Diatomite (MD) was achieved using a crosslinking system based on a mixture of sulfur, accelerator, and peroxide. The iPP/Diatomite composite was prepared by batch melt mixing in a Brabender Plasti-Corde under intense shearing at high temperatures and varying the Diatomite content from 0 to 15 wt%. The rheological behavior was examined by monitoring the Brabender Plasti-Corde torque/time rheographs. Different techniques were used to characterize the sample: Fourier transform infrared spectroscopy (FTIR), WAXS, SEM, and DSC. In addition, tensile strength tests and impact strength mechanical tests were conducted to study the performance. It was found that chemical modification strongly affected rheological behavior and generated a new rheological characteristic compared to the composites without modification. This has induced a new structure form that has improved mechanical properties. Moreover, the chemical modification used and due to its simplicity, can be successfully used on an industrial scale with the appropriate process.

Structural design of a new XLPE Insulation material without cross-linking by-products and theoretical study on the reaction mechanism: An alternative to peroxide crosslinking

The cross-linked polyethylene (XLPE) is used in most advanced power cable insulation. The cross-linking byproducts based on typically dicumyl peroxide (DCP) cross-linking process increase the electrical conductivity of the insulation material. In order to remove the hazardous byproducts, an essential time-consuming and energy-consuming procedure is needed. Hence, a new XLPE production process without cross-linking by-products receives considerable attention. Here, the structural design of a new XLPE based insulation materials have been established. The cross-linking of epoxy and reactive functional groups between two polyethylene copolymers in situ through reactive compounding is an alternative to DCP crosslinking without cross-linker and byproducts. Theoretical investigation on the reaction process of covalent bonds forming and reaction mechanism is accomplished by density functional theory. Two reaction mechanisms, synergistic reaction and step-by-step reaction, are proposed. The reaction potential energy information of the twelve reaction channels at B3LYP/6–311 +G(d,p) level are obtained. The calculation results show that the epoxy and reactive functional groups between two poly-ethylene copolymers can react in situ and crosslink through the formation of covalent bond to realize the networking of XLPE. The reaction of maleic anhydride with H2O (or CH3OH) is more kinetically and thermodynamically favorable than that of maleimide. The reactivity of carboxylic acid functional group is stronger among three cross-linking reaction systems considered. The reaction Gibbs energy barrier heights of synergistic reaction are lower than that of step-by-step reaction by about 0.6 eV. The theoretical study on the reaction mechanism of epoxy and reactive functional groups between two polyethylene copolymers would be beneficial to avoid the forming of hazardous cross-linking byproducts, which is a promising method to design thermoplastic insulation materials for future power cables.

A biodegradable cellulose fibrous membrane comprising cellulose microfibers and nanofibrils with enhanced interaction through crosslinking structure

AbstractThe petroleum‐based materials are widely used in daily life, which are inherently tough to degrade, increasingly polluting the environment and affecting human health. Cellulose fibrous membrane, the ubiquitous, low‐cost, and biodegradable material, can serve as a promising substitute. Herein, the biodegradable cellulose fibrous membranes were constructed with cellulose microfibers made from wood particle fibers (WPF) and the mechanical properties were enhanced by introducing the crosslinking system. The cellulose fibrous membrane made of the original WPF showed low tensile strength (0.1 KPa) and elastic modulus (1 MPa). By adding 10 wt% cellulose nanofibrils (CNFs), the prepared cellulose fibrous membrane exhibited an increase in tensile strength (0.525 MPa) and elastic modulus (535 MPa), respectively. To further improve the mechanical properties, the sodium alginate (SA) and Ca2+ were introduced to crosslink with the CNFs and promote the interaction among SA, CNFs and microfibers, which resulted in a substantial increase in tensile strength (5.62 MPa) and elastic modulus (1660 MPa) due to the formation of the interpenetrating entanglements and anchors. The normalized fracture energy of crosslinked hybrid cellulose fibrous membrane was 100.38 times higher than that of the original WPF membrane and 16 times higher than that of the un‐crosslinked cellulose membrane comprising CNFs. This strategy can serve as the foundation for preparing a mechanically enhanced cellulose fibrous membrane via crosslinking, making it possible to replace petroleum‐based plastics.

Insights into Uniaxial Tension and Relaxation of Nanorod-Filled Polymer Vitrimer Nanocomposites: A Molecular Dynamics Simulation

The mechanical properties of polymer nanocomposites (PNCs) depend sensitively on the structure (e.g., orientation, dispersion, and so on) of the incorporated nanofillers. Many studies have shown that the alignment of anisotropic nanofillers can improve the mechanical properties of PNCs. However, achieving this alignment typically requires complex preparation processes. To address this challenge, researchers have introduced dynamic covalent bonds to form reversible cross-linked polymer systems, which would lead to unique properties, such as self-healing, recyclability, and reprocessibility. In addition, inspired by the above ideas, we introduce nanorods as fillers into a linear vitrimer system to form nanorod vitrimer composites (NVCs). In NVCs, we can easily manipulate the alignment of the nanorods due to bond exchange reactions (BERs) in the vitrimer matrices. By using coarse-grained molecular dynamics (CGMD) simulations, we systematically investigate the factors affecting the nanorod orientation in NVCs. We find that the main factor affecting the nanorod orientation is the network rearrangement caused by BERs. Specifically, the BER potential barrier (ΔEsw) directly determines the probability of BERs’ occurrence. At the same time, the increase of the interfacial interaction between polymer chains and nanorods (εnp) confines the motion of the active beads, which slows down the rate of BERs. Additionally, the impact of temperature (T) and aspect ratio (ld) on the orientation of nanorods during uniaxial stretching or stress relaxation are also discussed. Finally, by combining uniaxial stretching and stress relaxation processes, we elucidate the orientation retention mechanism of NVCs and demonstrate the mechanical property enhancement phenomenon of the pre-oriented NVC systems. This work provides a simple strategy for manipulating the nanorod alignment in vitrimer matrices and uncovers guidelines for designing new functional polymer vitrimer nanocomposites at the molecular level.

Epoxidized waste cooking oil enhancing the interfacial binding strength for fully bio-based flame retardant wool fabric with good wearability

Bio-based flame retardants have been widely studied for their eco-friendly, renewable and sustainable advantages. However, the durability of bio-based flame retardants is usually poor due to the weak combination with textile substrates. In this study, based on the strategy of constructing a covalent anchoring network between flame retardants and textile substrates, epoxidized waste cooking oil (EWCO) was used as the bio-based crosslinking agents to covalently bind with phytic acid (PA) and chitosan (CH) forming the fully bio-based intumescent flame retardant (IFR) system. The wool fabrics were treated by PA/EWCO/CH IFR system through simple pad-dry-cure finishing process, and a large cross-linking system between the flame retardants and wool fabrics could form during the finishing process anticipating to enhance the interfacial binding strength. The limited oxygen index (LOI) value of PA/EWCO/CH treated wool fabric reached 30.5%, its char length reduced to 96 mm showing excellent flame retardancy, and it still possessed good wearability. The LOI value of PA/EWCO/CH treated wool fabrics after 4 times washing was 27.5%, which was higher than that without EWCO (26.3%) showing good washing durability. This research provides a new strategy for solving the interfacial binding fastness between bio-based flame retardants and substrates to enhance the flame retardant durability by using bio-based waste plant oil derivatives crosslinking agent.