Cross-linking Properties Research Articles

Preparation and Performance Evaluation of Weighted Gel Fracturing Fluid with Delayed Cross-Linking Property for Ultradeep Reservoir

Preparation and Performance Evaluation of Weighted Gel Fracturing Fluid with Delayed Cross-Linking Property for Ultradeep Reservoir

Lipoic acid-locked reduction-responsive core-cross-linked micelles delivering paclitaxel for triple-negative breast cancer treatment

Most anti-tumor agents suffer from systemic non-specific distribution and low aggregation in tumors, which not only decreases the therapeutic efficacy, but also causes systemic toxic side effects in the treatments of tumors. In recent years, the rapid development of nanotechnology has brought new ideas for the application of anti-tumor drugs. Nanomedicines, such as liposomes and micelles, can improve drug targeting and prolong systemic circulation time to promote anti-tumor efficacy and reduce toxic side effects. However, conventional micelles bear the risk of instability and premature drug leaking in the blood circulation. We designed a reduction-responsive core-cross-linked micelle PTX@Fmoc-LA-PEG efficiently encapsulating Paclitaxel (PTX) via π-π stacking and hydrophobic interactions of Fmoc and PTX. Moreover, the micelle was further locked based on the cross-linking properties of the disulfide bonds formed by lipoic acid (LA). As expected, the core-cross-linked micelles PTX@Fmoc-LA-PEG remained stable in normal physiological environments, while restoring the normal drug release rate of micelles under the highly reducing environment due to LA unlocking. The blank micelles (Fmoc-LA-PEG) exhibited excellent biocompatibility, while the drug-loaded micelles (PTX@Fmoc-LA-PEG) displayed a remarkable anti-tumor effect in vitro and in vivo experiments. These results suggested that core-cross-linked micelles PTX@Fmoc-LA-PEG have great potential to improve the targeting and stability of anti-tumor drugs.

Exploiting the Potential of Iridium(III) bis-Nitrone Complexes as Phosphorogenic Bifunctional Reagents for Phototheranostics.

Cross-linking strategies have found wide applications in chemical biology, enabling the labeling of biomolecules and monitoring of protein-protein interactions. Nitrone exhibits remarkable versatility and applicability in bioorthogonal labeling due to its high reactivity with strained alkynes via the strain-promoted alkyne-nitrone cycloaddition (SPANC) reaction. In this work, four cyclometalated iridium(III) polypyridine complexes functionalized with two nitrone units were designed as novel phosphorogenic bioorthogonal reagents for bioimaging and phototherapeutics. The complexes showed efficient emission quenching, which is attributed to an efficient nonradiative decay pathway via the low-lying T1/S0 minimum energy crossing point (MECP), as revealed by computational studies. However, the complexes displayed significant emission enhancement and lifetime extension upon reaction with (1R,8S,9s)-bicyclo[6.1.0]non-4-yne (BCN) derivatives. In particular, they showed a remarkably higher reaction rate toward a bis-cyclooctyne derivative (bis-BCN) compared with its monomeric counterpart (mono-BCN). Live-cell imaging and (photo)cytotoxicity studies revealed higher photocytotoxicity in bis-BCN-pretreated cells, which is ascribed to the enhanced singlet oxygen (1O2) photosensitization resulting from the elimination of the nitrone-associated quenching pathway. Importantly, the cross-linking properties and enhanced reactivity of the complexes make them highly promising candidates for the development of hydrogels and stapled/cyclized peptides, offering intriguing photophysical, photochemical, and biological properties. Notably, a nanosized hydrogel (2-gel) demonstrated potential as a drug delivery system, while a stapled peptide (2-bis-pDIKK) exhibited p53-Mdm2 inhibitory activity related to apoptosis and a cyclized peptide (2-bis-RGD) showed cancer selectivity.

2K/UV dual-curable acrylate epoxy/SiO2 nanocomposite coatings: crosslinking and mechanical properties

2K/UV dual-curable acrylate epoxy/SiO2 nanocomposite coatings: crosslinking and mechanical properties

Modulation of Mechanical Properties of Silica-Filled Silicone Rubber by Cross-Linked Network Structure.

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory-Rehner model and Mooney-Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber.

Current Review: Alginate in the Food Applications

Due to global development and increased public awareness of food’s effects on health, demands for innovative and healthy products have risen. Biodegradable and environmentally friendly polymer usage in modern food products is a promising approach to reduce the negative health and environmental effects of synthetic chemicals. Also, desirable features such as flavor, texture, shelf-life, storage condition, water holding capacity, a decrease in water activity, and an oil absorption of fried food have been improved by many polysaccharides. One of the important polymers, which is applied in the food industry, is alginate. Alginates are a safe and widely used compound in various industries, especially the food industry, which has led to innovative methods for for the improvement of this industry. Currently, different applications of alginate in stable emulsions and nano-capsules in food applications are due to the crosslinking properties of alginate with divalent cations, such as calcium ions, which have been studied recently. The main aim of this review is to take a closer look at alginate properties and applications in the food industry.

Immobilization of l-asparaginase on genipin cross-linked chitosan beads shows better acrylamide diminution in cassava chips: Process optimization and characterization.

Glutaraldehyde is the conventionally used cross-linker for the activation and cross-linking of support matrices used in enzyme immobilization. However, the toxic nature of glutaraldehyde makes it unsafe for food applications, propelling the need for nontoxic cross-linkers. Genipin reacts with the primary and secondary amines generating a dark-blue colored pigment and is an attractive alternative to glutaraldehyde as a cross-linker for enzyme immobilization. Apart from its excellent cross-linking properties, genipin possesses added advantages over glutaraldehyde such as proven health benefits, biocompatibility, and biodegradability. The present study explores the application of chitosan beads cross-linked with the natural and nontoxic agent, genipin, for immobilizing l-asparaginase, aimed at its subsequent use in mitigating acrylamide formation in food products. The immobilized l-asparaginase exhibited improved functionalities such as stability, reusability, and reduction in acrylamide formation in deep-fried cassava chips. One of the limitations observed during application in the food process was the mechanical fragility of the chitosan beads during speedy stirring. This can be overcome by increasing the concentration and time of contact of the coagulant bath during the formation of chitosan beads. The drying of the enzyme-bound chitosan beads will also lead to shrinkage and prevent breakage during stirring. This study conclusively demonstrated the applicability of immobilizing l-asparaginase on genipin cross-linked chitosan beads in food-related processes.

Synthesis of a water‐soluble high hydroxymethyl content phenolic resin crosslinker and the associated polyacrylamide weak gel property investigation

AbstractAs an in‐depth profile control agent, water‐soluble phenolic resin crosslinking polyacrylamide weak gel has been widely used in the middle and high water cut stage of water flooding reservoir. In this study, the phenolic resin was synthesized by two‐step alkali catalysis. Factors influencing the synthesis of phenolic resin, including the molar ratio of phenol and formaldehyde, catalyst types, reaction time, were investigated with hydroxylmethyl and aldehyde content as the criterion. When the molar ratio of phenolic resin was 1:2 and NaOH was catalyst, at 80°C for 4 h, the phenolic resin had the highest hydroxymethyl content (49.37%) and the lowest free aldehyde content (2.95%). Weak gel was formed by the reaction of LT002‐polyacrylamide with phenolic resin. Taking the gelation time and strength as criteria, the factors influencing the crosslinking property, including hydroxymethyl content, crosslinker addition, and polyacrylamide concentration were investigated respectively. Under optimal formulation, the property investigation shows that the hydroxymethyl group in the phenolic resin can be crosslinked with the amide group in polyacrylamide, the gelation time is long (50–60 h), and the gelation strength is larger than 5 × 104 mPa s, which is conductive to the plugging of deep oil layers. When the permeability was 5061 × 10−3 μm2, the plugging rate was 72.73%.

Tannic acid/polyethyleneimine functionalized hexagonal boron nitride: Enhancing tribological properties of epoxy-based composite coatings

The interfacial compatibility issue of boron nitride (BN) nanofillers in epoxy resin (EP) matrix is one of the major challenges plaguing the efficient application of composites. Herein, inspired by phenol-amine green chemistry, microwave-assisted ball milling was used to synthesize tannic acid (TA) and polyethyleneimine (PEI) functionalized boron nitride (TA/PEI@BN). Characterization indicated that TA/PEI grafted on BN via both non-covalent and covalent interactions, which improved the interfacial compatibility and cross-linking properties of TA/PEI@BN within the EP. Meanwhile, the introduction of 0.25 % TA/PEI@BN reduced the average friction coefficient and wear rate of the EP composite coating by 17 % and 50 %, respectively. The characterization of the friction interface showed that TA/PEI@BN could exhibit a "sliding complementary repair" effect during friction. This work presents a novel, green, and scalable method for realizing the surface functionalization of BN, beneficial for the further application of high-performance epoxy matrix composites.

Six-membered ring-reinforced flexible high-elongation block polyamide as strong and multi-reusable hot melt adhesive

This study presented the synthesis and characterization of polyester block polyamide hot melt adhesives (PPHMAs) with high adhesion strength and toughness. The PPHMAs demonstrated an adhesion strength of 11.04 MPa and toughness of 22.54 MJ·m−3, making them suitable for various substrates such as aluminum, copper, and stainless steel. The polyamide segments synthesized from dimer acid and 2-methyl-1,5-diaminopentane exhibited characteristics of softness and high elongation. Using isophorone diamine as a reinforcing agent introduced a stable six-membered ring structure, which enhanced the polymer's rigidity and strength, thus meeting the requirements for polyamide segments to function as the hard segments in block polymers. A trace amount of Tris (2-aminoethyl) amine provided the cross-linking sites which are similar to those in neuronal structures. The polyester segments, which were synthesized from poly (propylene glycol) diglycidyl ether and sebacic acid, served as the soft segments in the block polymer and were connected to the hard segment via amide bonds. The addition of the polyester segments enhanced the non-covalent molecular interactions within PPHMAs, leading to dynamic crosslinking properties. The adhesive maintained stable adhesion even after six cycles, which showcased its durability. Furthermore, the PPHMAs exhibited notable chemical resistance. It retained over 60 % adhesion strength after exposure to some chemical solvents including artificial seawater, 5 % NaOH solution, 5 % HCl solution, and DMSO for 24 h. These findings offered a novel approach to enhancing the adhesion strength and toughness of conventional thermoplastic hot melt adhesives.

Construction of Tough Hydrogel Cross-Linked via Ionic Interaction by Protection Effect of Hydrophobic Domains.

Most hydrogels have poor mechanical properties, severely limiting their potential applications, and numerous approaches have been introduced to fabricate more robust and durable examples. However, these systems consist of nonbiodegradable polymers which limit their application in tissue engineering. Herein, we focus on the fabrication and investigate the influence of hydrophobic segments on ionic cross-linking properties for the construction of a tough, biodegradable hydrogel. A biodegradable, poly(γ-glutamic acid) polymer conjugated with a hydrophobic amino acid, l-phenylalanine ethyl ester (Phe), together with an ionic cross-linking group, alendronic acid (Aln) resulting in γ-PGA-Aln-Phe, was initially synthesized. Rheological assessments through time sweep oscillation testing revealed that the presence of hydrophobic domains accelerated gelation. Comparing gels with and without hydrophobic domains, the compressive strength of γ-PGA-Aln-Phe was found to be six times higher and exhibited longer stability properties in ethylenediaminetetraacetic acid solution, lasting for up to a month. Significantly, the contribution of the hydrophobic domains to the mechanical strength and stability of ionic cross-linking properties of the gel was found to be the dominant factor for the fabrication of a tough hydrogel. As a result, this study provides a new strategy for mechanical enhancement and preserves ionic cross-linked sites by the addition of hydrophobic domains. The development of tough, biodegradable hydrogels reported herein will open up new possibilities for applications in the field of biomaterials.

Preparation of Cross-Linked Sodium Alginate Microspheres with Different Metal Ions Using the Microfluidic Electrospray Technology.

Microspheres are micrometer-sized particles that can load and gradually release drugs via physical encapsulation or adsorption onto the surface and within polymers. In the field of biomedicine, hydrogel microspheres have been extensively studied for their application as drug carriers owing to their ability to reduce the frequency of drug administration, minimize side effects, and improve patient compliance. Sodium alginate (ALG) is a naturally occurring linear polysaccharide with three backbone glycosidic linkages. There are two auxiliary hydroxyl groups present in each of the moieties of the polymer, which have the characteristics of an alcohol hydroxyl moiety. The synthetic ALG units can undergo chemical cross-linking reactions with metal ions, forming a cross-linked network structure of polymer stacks, ultimately forming a hydrogel. Hydrogel microspheres can be prepared using a simple process involving the ionic cross-linking properties of ALG. In this study, we prepared ALG-based hydrogel microspheres (ALGMS) using a microfluidic electrodeposition strategy. The prepared hydrogel microspheres were uniformly sized and well-dispersed, owing to accurate control of the microfluidic electrospray flow. ALGMS cross-linked with different metal ions were prepared using a microfluidic electrospray technique combining microfluidic and high electric field, and its antimicrobial properties, slow drug release ability, and biocompatibility were investigated. This technology holds promise for application in advanced drug development and production.

Physicochemical evaluation of polyvinyl alcohol films crosslinked with saturated and unsaturated dicarboxylic acids: A comparative study

AbstractIn this study, crosslinked films of polyvinyl alcohol (PVA) were prepared using two dicarboxylic acids: saturated succinic acid (SA) and unsaturated maleic acid (MAL) as crosslinkers. The crosslinking capabilities of these acids were compared through physical, chemical, mechanical, morphological, thermal analysis, and swelling measurements to investigate their impact on the physicochemical properties of the resulting films. Attenuated total reflectance fourier transform infrared spectroscopy (FTIR) confirmed the occurrence of an esterification reaction between PVA and the dicarboxylic acids. Based on the degree of crosslinking and thermal properties, it was noted that the crosslinking achieved with maleic acid is more effective for PVA compared with succinic acid. The crosslinking degree of PVA‐MAL was determined to be 6.47 times higher than that of the PVA‐SA film. In terms of thermal stability, the decomposition temperature for crosslinked PVA‐MAL was measured at 365.57°C, whereas PVA‐SA exhibited a slightly lower decomposition temperature of 362.58°C. The findings indicate that the PVA‐MAL film displays lower crystallinity and a higher contact angle (80.60°) in contrast to PVA‐SA (76.0°) and PVA (30.4°). Atomic force microscopy analysis indicated that the PVA‐SA film exhibited more surface roughness compared with the smoother PVA‐MAL film. Also, crosslinked films displayed enhanced elasticity and resilience in comparison with neat PVA, which may be due to the difference in crosslinking density, disruption in intermolecular hydrogen bonding due to crosslinking, and incorporation of flexible crosslinkers.Highlights PVA was crosslinked using SA and MAL. Unsaturated MAL exhibited superior crosslinking density over saturated SA. PVA‐SA film exhibited a porous surface compared to PVA‐MAL film. PVA crosslinked with unsaturated MAL showed higher thermal stability than SA. Both the films showed enhanced elasticity and resilience compared with neat PVA.

Shape-fixing hydrogel promotes scarless healing of wounds under tension

The healing of a wound under tension (hereafter, “tension wound”) often coincides with the development of hypertrophic scars in clinical settings. Currently, compress bandages offer a potential alternative for the healing of tension wounds; however, their application in surgery is limited due to their prefabricated patch form. To overcome this, a tension-shielding hydrogel system was designed using photocurable catechol-grafted hyaluronic acid and tannic-acid silver nanoparticles (hereafter, “HTA system”). The hydrogel exhibited tension-shielding capacity, reducing wound tension via shape-fixation and ultimately reducing scar formation. The HTA hydrogel exhibited superior photothermal antibacterial efficacy, self-healing properties, and effective dissipation of energy, thereby promoting tissue regeneration. The hydrogel significantly inhibited the mechanotransduction pathway, thus preventing Engrailed-1 activation and reducing the fibrotic response. The HTA hydrogel system, therefore, provides a treatment strategy for tension wounds, burn wounds and other wounds that are prone to form hypertrophic scars via creating a tension-free local environment. Statement of significanceIn our study, we presented a wound-dressing hydrogel system (HTA) that exhibit shape-fixing capacity in tension wound model. Here, we designed and modified a tension regulator, applied it to mice, and furthermore, established a tension wound model in mice with adjustable tension. Outcomes showed that the HTA hydrogel system can effectively form a shape-fixed environment on tension wounds and dynamic wounds, thus promoting scarless healing. Additionally, HTA performs injectability, rapid crosslinking, biocompatibility, wet adhesion, hemostasis and photothermal antibacterial properties. We believe this research has various potential clinical applications, including scarless-healing in tension wounds, treatment of acute bleeding, treatment of infected wounds, and even internal organ repair.

Gamma-irradiation-induced tailoring of physical, electrical, optical, and mechanical properties of PVC/PANI/TiO2 nanocomposites for different applications

Gamma irradiation exhibits a complex influence on the properties of PVC/PANI/TiO2 nanocomposite films. XRD analysis reveals a non-monotonic response in crystallinity, with an initial increase at lower doses due to crosslinking followed by a decrease at higher doses attributed to polymer chain scission. Mechanical properties exhibit an improvement in tensile strength and Young's modulus at moderate doses (up to 100 kGy) due to crosslinking. However, excessive irradiation (>100 kGy) induces chain degradation, causing a decrease in both tensile strength and elongation at break. Similar dose-dependent behavior is observed in thermal properties, with moderate doses improving thermal stability and melting temperature before a decline at higher doses due to chain degradation. Gamma irradiation significantly affects AC conductivity, suggesting potential changes in structure, charge carrier density, and conduction mechanisms. While the core chemical structure remains largely unaffected, FTIR and UV–Vis spectroscopy analyses indicate alterations in the degree of crosslinking and optical properties, warranting further investigation. Refractive index increases with irradiation due to enhanced density and changes in polarizability. This study highlights the importance of tailoring the gamma irradiation dose to achieve desired properties in PVC/PANI/TiO2 nanocomposite films for various applications.

Optimizing Eriochrome Black T adsorption through In-Situ polymerization of Poly(aniline-co-formaldehyde) on biochar: Multivariate approach using full factorial Design, Box-Behnken, Artificial intelligence, and DFT

Over the past few years, using organic–inorganic composites in wastewater treatment through adsorption has become increasingly widespread. The combination of activated carbon and polyaniline (AC@PANI) has garnered significant interest in these composites. This study introduces a novel type of coating known as poly(aniline-co-formaldehyde) (PAF), which is classified as a copolymer and exhibits crosslinking properties. Compared to polyaniline, PAF forms a three-dimensional network structure, a rapid process for the synthesis of AC@PAF. Moreover, PAF demonstrates a notable enhancement in adsorption capacity for the anionic Eriochrome Black T (EBT) dye. In this study, we coated activated carbon, previously activated using H3PO4 (ACNgG-P), with PANI and PAF. Our findings reveal that the PAF coating exhibits an exceptional adsorption capacity of 700.01 mg/g for EBT, surpassing ACNgG-P and ACNgG-P@PANI.Furthermore, the adsorption of EBT onto the surface of ACNgG-P@PAF was optimized and modeled using artificial intelligence (AI), specifically an artificial neural network (ANN). The ANN was employed to predict and maximize adsorption by analyzing the complex relationships between various parameters. Finally, the Density Functional Theory calculations were used to elucidate the adsorption mechanism by identifying the active sites on the surface of ACNgG-P@PAF and analyzing the molecular structure of EBT.

Theaflavin -3,3'-digallate/ethanol: a novel cross-linker for stabilizing dentin collagen.

To study the ability of theaflavin-3,3'-digallate (TF3)/ethanol solution to crosslink demineralized dentin collagen, resist collagenase digestion, and explore the potential mechanism. Fully demineralized dentin blocks were prepared using human third molars that were caries-free. Then, these blocks were randomly allocated into 14 separate groups (n = 6), namely, control, ethanol, 5% glutaraldehyde (GA), 12.5, 25, 50, and 100mg/ml TF3/ethanol solution groups. Each group was further divided into two subgroups based on crosslinking time: 30 and 60s. The efficacy and mechanism of TF3's interaction with dentin type I collagen were predicted through molecular docking. The cross-linking, anti-enzymatic degradation, and biomechanical properties were studied by weight loss, hydroxyproline release, scanning/transmission electron microscopy (SEM/TEM), in situ zymography, surface hardness, thermogravimetric analysis, and swelling ratio. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were utilized to explore its mechanisms. Statistical analysis was performed using one and two-way analysis of variance and Tukey's test. TF3/ethanol solution could effectively crosslink demineralized dentin collagen and improve its resistance to collagenase digestion and biomechanical properties (p < 0.05), showing concentration and time dependence. The effect of 25 and 50mg/ml TF3/ethanol solution was similar to that of 5% GA, whereas the 100mg/mL TF3/ethanol solution exhibited better performance (p < 0.05). TF3 and dentin type I collagen are mainly cross-linked by hydrogen bonds, and there may be covalent and hydrophobic interactions. TF3 has the capability to efficiently cross-link demineralized dentin collagen, enhancing its resistance to collagenase enzymatic hydrolysis and biomechanical properties within clinically acceptable timeframes (30s/60s). Additionally, it exhibits promise in enhancing the longevity of dentin adhesion.

Strong and tough conductive hydrogels via an amphiphilic macromolecular crosslinker for flexible strain sensor

The strength and toughness of hydrogel are usually achieved through the synergy of chemical cross-linking and physical cross-linking from multi-component contributions. However, there are few reports on hydrogels that rely on a single component to obtain two cross-linked structures. Herein, we successfully synthesized an amphiphilic macromolecular crosslinker (polyoxyethylene 20 oleyl ether acrylate (O20AC)), and introduced it into a system composed of acrylamide (AAm), sodium chloride (NaCl) and water to prepare the P(AAm-O20AC)/NaCl hydrogel with high strength, outstanding toughness, and excellent good conductivity. Notably, the O20AC possess both crosslinker properties, which not only provide hydrogels with a stable chemical cross-linking network, but also its long hydrophobic chain act as physical crosslinking points to give the hydrogel a new pathway of energy dissipation.Depending on the O20AC crosslinker, the P(AAm-O20AC)/NaCl hydrogels exhibit good strength (tensile stress 714.46 kPa), toughness (elongation at break 3005 %), and fatigue resistance (overlap of hysteresis curves in repeated loading–unloading cycles). Besides, the existence of sodium ions and chloride ions also provides the hydrogel with highly sensitive deformation-dependent conductivity (GF is 5.8 in the 400 %-500 % strain range). Collectively, the strategy of preparing chemical and physical double-crosslinked hydrogels by amphiphilic O20AC will provide a bran-new insights for the development of hydrogel sensing materials.

Gradually Self-Strengthen DNA Supramolecular Hydrogels.

The dynamic mechanical strength of the extracellular matrix (ECM) has been demonstrated to play important role in determining the cell behavior. Growing evidences suggest that the gradual stiffening process of the matrix is particularly decisive during tissue development and wound healing. Herein, a novel strategy to prepare hydrogels with gradually enhanced mechanical strength is provided. Such hydrogels could maintain the dynamic properties at their initial states, such as self-healing and shear-thinning properties. With subsequent slow covalent crosslinking, the stability and mechanical properties would be gradually improved. This method is useful for sequence programmability and oxidation strategies, which has provided an alternated tool to study cell behavior during dynamic increase in mechanical strength of ECM.

Novel Mussel‐Inspired High‐Temperature Resistant Gel with Delayed Crosslinking Property for Ultra‐Deep Reservoir Fracturing

AbstractMussel‐inspired materials have been widely studied due to their excellent adhesion and self‐healing properties, but few studies have introduced this interesting property into the fracturing development of deep/ultra‐deep oil and gas fields. Herein, a new type of mussel‐inspired delayed crosslinking gel fracturing fluid is reported, which is formed by mussel‐inspired polymers containing many catechol groups and organic zirconium delayed crosslinkers. The strong supramolecular interaction in mussel‐inspired polymers can construct a more complex and stable dually cross‐linked polymer network based on conventional chemical crosslinking, to cope with harsh conditions such as high temperature and shear in reservoirs. After shearing at 200 °C, the reserved viscosity of mussel‐inspired delayed crosslinking gel is as high as 95 mPa·s. More importantly, the viscosity of gel remains basically unchanged at 25 °C, and the cross‐linking is completed within 300 s at 90 °C. The chemical force probe atomic force microscope (AFM) technology has successfully demonstrated that catechol groups are the main source of supramolecular interaction in mussel‐inspired polymers. The molecular simulation results show that due to the addition of catechol groups, the hydrogen bond interactions within the mussel‐inspired polymers molecules are enhanced. And the additional hydrogen bonds formed are more stable at high temperature.