Crosslinking Points Research Articles

Comprehensive crosslinking strategy using fluorinated azide to enhance the thermal stability of ceramic-coated separators for Li-ion batteries

Enhancing the thermal and mechanical stabilities of ceramic-coated separators (CCSs) is required for high-safety lithium-ion batteries (LIBs). As both the thickness and areal mass of ceramic coating layers (CCLs) have reduced, various strategies have been developed to overcome the limitations of conventional ceramics and polymeric binders. In this regard, we suggest a comprehensive photocrosslinking approach to form fully crosslinked CCLs using a new fluorinated azide binder that can readily react with aliphatic functional groups in any component of CCSs. When a small amount of azide binder is added to a CCL slurry consisting of Al2O3 particles and a poly(acrylic acid) (PAA) binder, short UV irradiation can lead to inter- and intramolecular crosslinking points within the polyethylene (PE) separator, between the PE separator and the PAA binder, and within the PAA binders in the CCL. Consequently, the thermal stability and the adhesive strength of crosslinked CCS (X-CCS) can be significantly improved compared to the control CCS without azide. Moreover, a LiNi0.6Co0.2Mn0.2O2/graphite cell with X-CCS exhibited a comparable cycle life to that of the PE separator and non-crosslinked CCS. Furthermore, because UV illuminators are easily added to conventional fabrication processes, this strategy is a simple but effective approach for advancing high-safety LIBs.

Preparation of fully physically crosslinked double-network gel and its fire prevention mechanism

It is important to gain an in-depth understanding of the structure of fire prevention and extinguishing materials during self-heating of coal. In this paper, an Al3+-CMC/PAM-MMT fire prevention and extinguishing gel with double-network was prepared using sodium carboxymethyl cellulose (CMC) and polyacrylamide (PAM) as raw materials, and aluminum citrate (AlCit) and sodium montmorillonite (Na-MMT) as auxiliary materials, by introducing the fully physically crosslinking effect. The optimal amounts of CMC, PAM, AlCit and MMT were determined to be 2 %, 3 %, 8 %, and 3 %, respectively, based on gelation time, stability, and resistance of the gel. The micromorphological image of the double-network gel exhibited a laminar structure of parallel-aligned fibrous networks, where the pores and channels exhibited more complex shapes and became smaller in size, highlighting the superiority of the double-network architecture. The rheological tests showed that the double-network gel had superior structural stability and viscosity under varying shear rates, making it more effective in covering the fire source, enhancing extinguishing efficiency. Additionally, its higher storage and loss moduli indicated stronger elasticity and mechanical properties compared to the single-network gel, emphasizing its advantages in energy storage and recovery. The characterization of active functional groups showed that there was an effective suppression of reactions involving hydroxyl, hydrocarbon, and carbonyl functional groups, during the spontaneous combustion process of coal, following treatment with the gel. Additionally, a proposed mechanism for the gel formation was presented. In the sealing performance test, the pressure-bearing capacity of the double-network gel was approximately twice that of the single-network gel. It indicated that the multi-level structure formed by the gel led to higher density of physical cross-linking points, which provided better sealing performance. Thermogravimetric analysis showed significant decrease in total calorific value and increase in activation energy of coal, after treatment with the gel, rendering it more difficult for spontaneous coal combustion. In the small-scale fire extinguishing performance test, the double network of Al3+-CMC/PAM-MMT gel demonstrated effective suppression of spontaneous combustion of coal and reduced the susceptibility to re-ignition. The fire prevention mechanism of the gel was further explored experimentally.

Unmatched resilience and fatigue resistance in a novel cellulose-derived ionic gel with hierarchical superstructured synergy for advanced human-computer interaction

Unlike traditional hydrogels, solvent-free ionic gels eliminate leakage and solvent volatilization, making them suitable for applications in electronic skin, sensing, and other fields due to their excellent conductivity and flexibility. However, designing solvent-free ionic gels with exceptional fatigue resistance, high ionic conductivity, and toughness remains a significant challenge. We address this challenge by employing small molecule/polymer heating self-assembly to regulate the synergistic effects of various components on the hierarchical superstructure. A multi-stage network was formed through the free radical polymerization of 3-Ethyl-1-vinyl-1H-imidazol-3-ium bromide ([C2VIm]Br), lipoic acid (LA), acrylic acid (AA), and hydroxypropyl cellulose (HPC), stabilized by dense hydrogen bonding and polymer chain entanglement. The resulting HPC/LA/AA/iLs (HLAI) ionic gel exhibits exceptional properties: excellent flexibility (with an elongation at break of 4222 %), toughness (1.03 MJ/m3), high ionic conductivity (3.29 × 10−2 S/m), and outstanding fatigue resistance (with a resilience of 91.9 % after 1000 load-unloading cycles at 50 % strain). Additionally, it shows low sensitivity to crack propagation (50 % notched sample can be stretched to 9 times without breaking) and good environmental stability, demonstrating excellent sensing sensitivity and stability (GF=3.23). The conductive ionic gel features a sophisticated hierarchical superstructure that synergistically enhances its properties at the molecular level. The integration of dynamic disulfide bonds, achieved through the polymerization of Lipoic acid, imparts remarkable self-healing capabilities and superior fatigue resistance. Additionally, the incorporation of a rigid HPC structure with dense cross-linking points bolsters elasticity, fracture resistance, and resilience. The gel’s ionic conductivity and sensing sensitivity are significantly enhanced by the inclusion of ionic liquids with polymerizable double bonds, making it an ideal material for applications requiring both flexibility and conductivity. This work presents a novel strategy for designing high-performance multi-stage network solvent-free ionic gels, opening up exciting possibilities for biomimetic electronic skin applications.

Methacrylated Wood Flour-Reinforced Gelatin-Based Gel Polymer as Green Electrolytes for Li-O2 Batteries.

With its very high theoretical energy density, the Li-O2 battery could be considered a valid candidate for future advanced energy storage solutions. However, the challenges hindering the practical application of this technology are many, as for example electrolyte degradation under the action of superoxide radicals produced upon cycling. In that frame, a gel polymer electrolyte was developed starting from waste-derived components: gelatin from cold water fish skin, waste from the fishing industry, and wood flour waste from the wood industry. Both were methacrylated and then easily cross-linked through a one-pot ultraviolet (UV)-initiated free radical polymerization, directly in the presence of the liquid electrolyte (0.5 M LiTFSI in DMSO). The wood flour works as cross-linking points, reinforcing the mechanical properties of the obtained gel polymer electrolyte, but it also increases Li-ion transport properties with an ionic conductivity of 3.3 mS cm-1 and a transference number of 0.65 at room temperature. The Li-O2 cells assembled with this green gel polymer electrolyte were able to perform 180 cycles at 0.1 mA cm-2, at a fixed capacity of 0.2 mAh cm-2, under a constant O2 flow. Cathodes post-mortem analysis confirmed that this electrolyte was able to slow down solvent degradation, but it also revealed that the higher reversibility of the cells could be explained by the formation of Li2O2 in the amorphous phase for a higher number of cycles compared to a purely gelatin-based electrolyte.

Hydrogels with high sacrifice efficiency of sacrificial bonds and with high strength and toughness due to dense entanglements of polymer chains

Introducing sacrificial bonds is a common method for increasing the toughness of hydrogels. Many sacrificial bonds have been extensively investigated, but the sacrifice efficiency has never been studied. In this study, polyacrylamide hydrogels with highly entangled polymer chains containing carboxyl–zirconium (–COO−–Zr4+) sacrificial bonds are prepared to study the effect of polymer chain entanglement on the sacrificial bond efficiency. Unlike chemical crosslinking points, the dense physical entanglements do not affect the toughness (∼43 MJ/m3) of hydrogels but significantly improve the tensile strength (by two times) and Young’s modulus (by six times). Physical entanglements enable the chains to slide and adjust the network structure under stress, which enables more polymer chains and sacrificial bonds to participate in the deformation process. Therefore, dense entanglements will greatly improve the sacrifice efficiency. However, a high density of chemical crosslinking points will limit the improvement in the sacrifice efficiency, which is attributed to the sliding limitations because of physical entanglement. The highly entangled polyacrylamide hydrogels toughened by –COO−–Zr4+ have an excellent load-bearing capacity. This study provides a novel strategy for designing hydrogels with ultra-high strength and toughness, which paves the way for the development of many hydrogels used in engineering materials.

LLZTO crosslinks form a highly stretchable self-healing network for fast healable all-solid lithium metal batteries

Flexible composite solid electrolytes (CSEs) show great potentials in high-energy all-solid-state lithium metal batteries owing to their easy fabrication, good electrochemical properties, and high safety. However, it remains challenging to achieve good interfacial compatibility between the inorganic fillers and polymer matrix, which affects the lithium-ion transport efficiency and electrochemical performances of CSEs. Herein, a dynamic crosslinked network with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanoparticles as the cross-linking point is proposed for fabrication of a rapidly self-healing flexible CSE, which is signed as SHENE. The amino groups in the 3-aminopropyltriethoxysilane modified LLZTO behave as the bridge sites to react with the copolymer of 2-hydroxyethyl methacrylate-g-4-formylbenzoic acid and poly (ethylene glycol) methoxy acrylate to form imine bonds, which effectively connect the organic/inorganic interface. Compared to the traditional physical contact, the covalent imine bonds can not only enhance the interaction between the two phases, but also improve the dispersion of the ceramic LLZTO nanoparticles. Additionally, the dynamic reversibility of imine bonds allows for enhanced mechanical strength and self-repairing capabilities of SHENE. Therefore, a Li||Li symmetrical cell assembled with SHENE can stably cycle for 5000 h at 0.05 mA cm−2 and 25 °C. The corresponding Li/SHENE/LiFePO4 full battery also exhibits good rate performance under various C-rates. Additionally, the Li/SHENE/LFP pouch cell exhibits superior safety under various abuse conditions. Therefore, this work provides new ideas for the uniform dispersion of ceramic nanoparticles in CSEs by the facile design of forming dynamic crosslinked networks.

Soft, Tough, Antifatigue Fracture Elastomer Composites with Low Thermal Resistance through Synergistic Crack Pinning and Interfacial Slippage.

Soft elastomer composites are promising functional materials for engineer interfaces, where the miniaturized electronic devices have triggered increasing demand for effective heat dissipation, high fracture energy, and antifatigue fracture. However, such a combination of these properties can be rarely met in the same elastomer composites simultaneously. Here a strategy is presented to fabricate a soft, extreme fracture tough (3316J m-2) and antifatigue fracture (1052.56J m⁻2) polydimethylsiloxane/aluminum elastomer composite. These outstanding properties are achieved by optimizing the dangling chains and spherical aluminum fillers, resulting in the combined effects of crack pinning and interfacial slippage. The dangling chains that lengthen the polymer chains between cross-linked points pin the cracks and the rigid fillers obstruct the cracks, enhancing the energy per unit area needed for fatigue failure. The dangling chains also promote polymer/filler interfacial slippage, enabling effective deflection and blunting of an advancing crack tip, thus enhancing mechanical energy dissipation. Moreover, the elastomer composite exhibits low thermal resistance (≈0.12K cm2 W-1), due to the formation of a thermally conductive network. These remarkable characteristics render this elastomer composite promising for application as a thermal interface material in electronic devices.

Thiolated nanoclays as a potential mucoadhesive material: Optimization by design of experiments and multivariate regression

An integrated strategy based on design of experiments (DoE) and multivariate regression was carried out to produce an optimized surface functionalized nanoclay (Mt–SH) with potential mucoadhesive properties. A mercaptosilane was grafted in montmorillonite in order to immobilize thiol groups (–SH) on the clay. The functionalization was confirmed by IR, TGA, XRF and XRD analyses. Five variables involved in the synthesis were optimized in order to maximize two responses: mass of functionalized nanoclay and amount of thiol groups attached in the clay surface. This optimization was performed by a two–step DoE strategy using Plackett–Burman and Box–Behnken designs. The five variables and two responses were simultaneously calibrated in a single ANOVA–validated PLS regression model. Analyzing scores, loading and surface response plots, the main processing variables, interactions and quadratic terms were found achieving the optimal processing conditions for the synthesis. The quadratic model (R2 > 0.8589) predicted an optimized functionalized nanoclay of mass 3.29 ± 0.13 g of Mt–SH with 19.65 ± 0.78 μmol –SH per g Mt–SH (P < 0.05). The optimized Mt–SH was evaluated by in vitro and in situ mucoadhesion assays with porcine mucin and fresh intestinal mucus by using rheometry. The complex viscosity showed an increase of ∼54-fold higher compared to the unmodified Mt, and ∼12.8-fold increase in the elastic modulus, which indicates a more resistance to elastic deformation probably due to an increase in cross-linking points between Mt–SH and mucus. The formation of disulfide bonds between thiol groups from Mt–SH and glycoproteins in the mucin could be a reasonably explanation which shows a correlation respect other thiolated materials which show the same mucoadhesion properties. These results could project this functionalized silicate material as a potential mucoadhesive prospect for pharmaceutical applications.

Biomimetic design of polyisoprene rubber with terminal synergistic effects leading to mechanical properties and creep resistance boost

The enhancement of polyisoprene rubber performance through biomimetic simulation of the terminal effect of natural rubber has been explored. So far, the presence of synergistic effects between different terminal groups and the challenge of controlling the relaxation behavior of non-covalent bonds while preserving their advantages remain open questions. In this study, we successfully prepared natural rubber biomimetic polymers with different functionalized terminals. Specifically, we constructed terminal-olefin cross-linking points at one end of the polymer chains, while dissociable oligopeptide assemblies were formed at the other end. Investigation of the viscoelastic behavior of the polymers and the structure of the rubber network confirmed the existence of synergistic effects between different terminal groups. The terminal-olefin cross-linking points effectively anchored the rubber network and stabilized the non-covalent bonds. Simultaneously, the non-covalent bonds formed by the oligopeptides acted as weak bonds, dissipating energy and improving the dimensional stability and mechanical properties of the vulcanized rubber.

Neural network inspired bionic ordered structure polyaniline gel for wearable sensor

In recent years, remarkable progress has been made in the research and development of traditional conductive polymer gel wearable sensors. However, it is still a challenge to achieve high sensitivity and mechanical strength at the same time due to the influence of the characteristics of conductive material in gels. Herein, inspired by human neural network, a novel biomimetic ordered polyaniline conductive gel is presented with stable conductivity (18.04 S/m), excellent sensitivity (GF of 3.53) under the condition of high elongation (stretching of 400 %-500 %), good mechanical properties, biocompatibility, and anti-freezing performance. This conductive gel is composed of maleic anhydride modified γ-cyclodextrin, polyaniline, and polyacrylamide. Modified γ-cyclodextrin can be firmly fixed on the polyacrylamide skeleton of the gel through chemical bonds. The aniline is evenly distributed in the hydrophobic cavity of modified cyclodextrin through hydrophobic interaction, and an ordered polyaniline network with γ-cyclodextrins as a physical crosslinking point is formed in the gel. This biomimetic ordered structure greatly improves the toughness and conductivity of the polyaniline network, which significantly enhances the sensing ability of polyaniline gels. This work is expected to provide a novel method for improving the mechanical and electrical properties of polyaniline gels and pave an avenue for the uniform dispersion of non-polar substances in polar gels.

Effect of corrosion on mode I fracture toughness and fracture behavior in A7075/CFRP adhesive bonded joints

The interlaminar fracture toughness of aluminum alloy/carbon fiber reinforced plastic (CFRP) joints subjected to accelerated aging due to corrosion was investigated over time. An acoustic emission (AE) measurement was performed as an evaluation method in conjunction with double cantilever beam testing. It was confirmed that the difference in the number of cross-linking points in the adhesive affected the fracture morphology and corrosion behavior, which resulted in a change in the fracture toughness. The AE measurements facilitated the visualization of the process zone and real-time monitoring of the fracture morphology, and they were able to capture changes in the fracture behavior with the corrosion progression.

Mechanical properties of composite materials with low-covered polyrotaxane and plasma-surface-modified hexagonal boron nitride

An effective method for fabricating flexible materials containing thermally conductive fillers, such as hexagonal boron nitride (hBN), utilizes plasma surface modification and polyrotaxane (PR) with movable cross-linking points. This study demonstrated that lowering the coverage rates of PR composites increased the mobility of the cross-linking points. Plasma surface modification improved the dispersion of hBN and enabled homogeneous deformation of the PR composites owing to movable cross-linking points. Studying the deformation with a model including a finite extension effect indicated that the sliding range in the low-covered PR composites was extended compared to that in the high-covered PR composites, resulting in a smaller Young’s modulus, longer extension, and higher toughness.

Hygrothermal aging mechanism of epoxy composites used for medium-frequency transformers

The integration of medium-frequency transformer design and the harsh service environment raise higher demands for the medium-frequency insulation performance of epoxy composites. As epoxy composite's frequency response characteristics and sensitivity to moisture intrusion are still unknown, its application as the insulation materials of medium-frequency transformers under hygrothermal conditions is limited. This paper investigates the mechanism of moisture intrusion damage to the molecular structure of the epoxy resin matrix and its cross-linking points with the curing agent. The regularity of medium-frequency insulation performance degradation of epoxy composites after hygrothermal aging is studied. Results indicate that after 40 days of hygrothermal aging, moisture together with high temperature damaged the main chain of the epoxy resin and its cross-linking points with the curing agent, resulting in a 23 °C decrease in the glass transition temperature and an 82 % decrease in cross-linking density of the epoxy composite. Moisture ionization and the increase of carriers due to epoxy resin hydrolysis lead to an increase in the amount of space charge. The temperature rise caused by dipole steering polarization facilitates the formation of internal conductive pathways in the epoxy composite, resulting in a 73 % decrease in the medium-frequency breakdown strength and a four-order magnitude decrease in the medium-frequency volume resistivity of the epoxy composite. This study can guide the insulation design of high-reliability medium-frequency transformers.

Dynamically reversible cross-linked polymer electrolytes with highly ionic conductivity for dendrite-free lithium metal batteries

High-safety PEO-based electrolytes have attracted widespread attention, but their inefficient conduction of Li ions and poor contact with electrode interfaces deteriorate the performances of rechargeable lithium metal batteries. Herein, we design a vitrimer polymer electrolyte (V-SPE-PEG) with abundant dynamic imine bonds via Schiff base reaction between aldehyde and ammonia, which achieves high ionic conductivity and good interfacial compatibility with lithium anode. The dynamic polymer network in V-SPE-PEG exhibits solid-state plasticity because reversible imine bonding reactions enable the integrity of the polymer network to be maintained while altering the cross-linked points under external stimuli. Therefore, this 3D dynamic cross-linked network effectively facilitates the polymer chain dynamics and meanwhile enhances ionic conductivity. Additionally, dynamic bond exchange fosters electrolyte flowability and self-healing during lithium deposition, promoting a tightly integrated electrode/electrolyte interface while inhibiting lithium dendrites growth. Consequently, lithium symmetric cells utilizing the V-SPE-PEG electrolyte demonstrate exceptional long-term cycling stability, surpassing 1100 h and exhibit outstanding ionic conductivity of 2.7 × 10−4 S cm−1 at 30 °C. The LiFePO4||Li battery maintains stable cycling performance at both 40 °C and 60 °C. This study introduces an innovative approach to designing solid-state electrolytes for lithium-metal batteries.

Physically Crosslinked Poly(methacrylic acid)/Gelatin Hydrogels with Excellent Fatigue Resistance and Shape Memory Properties.

Hydrogels endure various dynamic stresses, demanding robust mechanical properties. Despite significant advancements, matching hydrogels' strength to biological tissues and plastics is often challenging without applying potentially harmful crosslinkers. Using hydrogen bonds as sacrificial bonds offers a promising strategy to produce tough, versatile hydrogels for biomedical and industrial applications. Poly(methacrylic acid) (PMA)/gelatin hydrogels were synthesized by thermally induced free-radical polymerization and crosslinked only by physical bonds, without adding any chemical crosslinker. The addition of gelatin increased the formation of hydrophobic domains in the structure of the hydrogels, which acted as permanent crosslinking points. The increase in PMA and gelatin contents generally led to a lower equilibrium water content (WC), higher thermal stability and better mechanical properties. The values of tensile strength and toughness reached up to 1.44 ± 0.17 MPa and 4.91 ± 0.51 MJ m-3, respectively, while the compressive modulus and strength reached up to 0.75 ± 0.06 MPa and 24.81 ± 5.85 MPa, respectively, with the WC being higher than 50 wt.%. The obtained values for compressive mechanical properties are comparable with super-strong hydrogels reported in the literature. In addition, hydrogels exhibited excellent fatigue resistance and biocompatibility, as well as great shape memory properties, which make them prominent candidates for a wide range of biomedical applications.

Evaluation of optical and self-healing properties of Titania/ionic liquid/poly(butyl methacrylate) hybrid material based on thermally reversible Diels–Alder chemistry

ABSTRACT In this study, we report the development of a hybrid polymer material comprising poly(butyl methacrylate) and titania, which exhibits the three key elements of visible-light transparency, UV shielding, and self-healing. Nanodispersion of titania in the polymers was achieved using the sol – gel method using titanium propoxide as the raw material. Furthermore, by adding tetrabutylphosphonium chloride, an ionic liquid, we suppressed visible light absorption due to charge transfer between poly(butyl methacrylate) and titania, resulting in enhanced visible light transmittance. An approach involving crosslinking points comprising Diels – Alder functional groups was used to heal scratches in the hybrid material at 75°C for 30 min. Dynamic viscoelastic measurements and microscopic observations were conducted to investigate the self-healing mechanism. These findings suggested that this phenomenon occurred through the fluidization of the polymer matrix and the recombination reaction of the crosslinking points, which comprise Diels – Alder and titania. The development of intelligent materials with combined transparency, UV protection, and self-healing capabilities provides potential avenues for future research to enhance and broaden their versatile characteristics for widespread applications.

A novel nanocomposite hydrogel with excellent photo-thermal and enhanced antibacterial properties based on China wood oil soot for acute wound healing

A hydrogel intended for potential use in wound dressing necessitates specific properties, including notable self-healing abilities, mechanical durability, and the ability to combat bacteria to address muscle and skin damage effectively. Moreover, the hydrogel must exhibit superior tissue adhesiveness to ensure seamless integration with the wound tissue during practical application scenarios. In this study, a novel photothermal China wood oil soot (CWOS)--based hydrogel (CH) dressing with high-strength and excellent photothermal performance was developed. Unlike traditional synthetic polymer networks, the novel nano-crosslinker fabricated by the CWOS optimized the dispersion of crosslinking points in the polymer network, resulting in outstanding mechanical properties (2000 % stretchability, 1.88 MPa strength). Massively reversible interactions between metal coordination (Ag-S) and hydrogen bonds gave the hydrogel excellent self-healing behavior. Besides excellent adhesiveness and biocompatible ability, the CH hydrogel combined with near-infrared ray radiation endowed highly antibacterial, alleviated inflammation, promoted angiogenesis, and promoted acute wound healing. Briefly, this multifunctional hydrogel can potentially aid wound healing for patients susceptible to bacterial infections. Its versatile properties offer promising prospects for its application in treating acute wounds.

Self-healing and reprocessable biobased non-isocyanate polyurethane elastomer with dual dynamic covalent adaptive network for flexible strain sensor

Owing to the nontoxicity of monomers, non-isocyanate polyurethane elastomers have attracted considerable attention, yet the synthesis and functionalization are still challenging. Herein, self-healing and reprocessable biobased non-isocyanate polyurethane (NIPU) elastomers with dual dynamic covalent adaptive network (DDCAN) by disulfide bonds and dynamic imine bonds were synthesized as substrate for the construction of flexible strain sensor with MXene as conductive substance. The tensile strength and elongation at break of the NIPU elastomer were 3.22 MPa and 234 %, respectively. Thanks to the formation of DDCAN, the NIPU elastomer showed high healing efficiency of 97.5 % after healing at room temperature for 24 h. Interestingly, the NIPU elastomer possessed superior reprocessing capability and the tensile strength after three reprocessing cycles reached 136.1 % of the original one, which was attributed to the increase of crosslinking points caused by topological rearrangement. In addition, the NIPU elastomer-based flexible strain sensor exhibited fast response (response time = 60 ms) and excellent repeatability (1000 bending-releasing cycles) and was successfully applied for human motion detection and speech recognition. The findings in this work conceivably stand out as a new methodology for the preparation of biobased and functional elastomers, which will greatly promote the sustainable development and application of flexible electronics.

Hyperbranched Vitrimer for Ultrahigh Energy Dissipation.

Polymers are ideally utilized as damping materials due to the high internal friction of molecular chains, enabling effective suppression of vibrations and noises in various fields. Current strategies rely on broadening the glass transition region or introducing additional relaxation components to enhance the energy dissipation capacity of polymeric damping materials. However, it remains a significant challenge to achieve high damping efficiency through structural control while maintaining dynamic characteristics. In this work, we propose a new strategy to develop hyperbranched vitrimers (HBVs) containing dense pendant chains and loose dynamic crosslinked networks. A novel yet weak dynamic transesterification between the carboxyl and boronic acid ester was confirmed and used to prepare HBVs based on poly (hexyl methacrylate-2-(4-ethenylphenyl)-5,5-dimethyl-1,3,2-dioxaborinane) P(HMA-co-ViCL) copolymers. The -type of macromonomers, the crosslinking points formed by the dynamic covalent connection via the associative exchange, and the weak yet dynamic exchange reaction are the three keys to developing high-performance HBV damping materials. We found that P(HMA-co-ViCL) 20k-40-60 HBV exhibited ultrahigh energy-dissipation performance over a broad frequency and temperature range, attributed to the synergistic effect of dense pendant chains and weak dynamic covalent crosslinks. This unique design concept will provide a general approach to developing advanced damping materials.

Hyperbranched Vitrimer for Ultrahigh Energy Dissipation

AbstractPolymers are ideally utilized as damping materials due to the high internal friction of molecular chains, enabling effective suppression of vibrations and noises in various fields. Current strategies rely on broadening the glass transition region or introducing additional relaxation components to enhance the energy dissipation capacity of polymeric damping materials. However, it remains a significant challenge to achieve high damping efficiency through structural control while maintaining dynamic characteristics. In this work, we propose a new strategy to develop hyperbranched vitrimers (HBVs) containing dense pendant chains and loose dynamic crosslinked networks. A novel yet weak dynamic transesterification between the carboxyl and boronic acid ester was confirmed and used to prepare HBVs based on poly (hexyl methacrylate‐2‐(4‐ethenylphenyl)‐5,5‐dimethyl‐1,3,2‐dioxaborinane) P(HMA‐co‐ViCL) copolymers. The ‐type of macromonomers, the crosslinking points formed by the dynamic covalent connection via the associative exchange, and the weak yet dynamic exchange reaction are the three keys to developing high‐performance HBV damping materials. We found that P(HMA‐co‐ViCL) 20k‐40‐60 HBV exhibited ultrahigh energy‐dissipation performance over a broad frequency and temperature range, attributed to the synergistic effect of dense pendant chains and weak dynamic covalent crosslinks. This unique design concept will provide a general approach to developing advanced damping materials.