Natural polysaccharides have emerged as promising candidates for eco-friendly lubricant additives due to their excellent biodegradability and abundant polar functional groups. However, most plant-derived polysaccharides suffer from a limited density of active sites, challenging chemical functionalization, and inconsistent availability of raw material. Herein, sulfated Nostoc flagelliforme exopolysaccharides (EPS) was successfully prepared via the chlorosulfonic acid-pyridine method. Tribological tests demonstrated that sulfation modification dramatically enhanced the friction-reducing and anti-wear properties of N. flagelliforme EPS. At the optimal concentration of 1.0% (v/v) and 3 N load, the sulfated EPS aqueous solution achieved an ultra-low friction coefficient of 0.027 and reduced the wear volume by 99.9% compared with pure water. During the friction process, a dense composite lubricating film can be formed due to the tribochemical reactions occurred at the friction interface. Meanwhile, the abundant polar groups in the EPS promoted the formation of stable hydration layer, which, in synergy with the surface protective film, resulted in ultra-low friction and excellent anti-wear performance. This work provides a new approach for the development of natural polysaccharide-based lubricating materials.

Maintaining excellent mechanical properties across a wide temperature range, particularly at low temperatures, is essential for elastomeric sealing materials. At lower temperatures, the soft segment domains of polyurethane (PU) tend to become immobilized, while the hydrogen bonds in the hard segment domains can easily dissociate, posing a significant challenge for PU to achieve superior mechanical performance under these conditions. Here, we introduced aromatic amines containing amide groups into the hard domains which not only facilitated the formation of stable yet dynamic crosslinked structures but also promoted the development of high-density hydrogen bonds, resulting in a specific hard segment cluster structure. The resulting polyurethane urea (PUU) demonstrated outstanding mechanical properties and toughness. Among them, DBPUU elastomers exhibited excellent mechanical properties, with a tensile strength of 71.82 MPa and elongation at break of 660 % at room temperature, and maintained high strength and toughness under extreme environments of -50 degrees C and 80 degrees C. Additionally, DBPUU possesses excellent solvent resistance and fatigue durability, making it particularly suitable for elastomeric sealing applications. This unique hard segment cluster structure also imparts luminescent properties and exceptional shape memory performance. This work provides a design strategy for high-strength, tough elastomeric sealing materials across a wide temperature range, while the multifunctionality of PUU expands its potential applications in anti-counterfeiting and information encryption.

Intrinsic self-healing materials are crucial for preventing unexpected shutdowns and extending service life. However, such materials often fail to simultaneously achieve high strength, high-temperature resistance, and creep resistance, which severely limits their practical applications. Therefore, developing intrinsic self-healing materials that combine high strength and creep resistance remains a significant challenge. Inspired by the “pulley” mechanism, we introduce a “dual-dynamic nanobridge” structure containing dynamic imine and boroxine bonds into a “pulley-like” polyimide network to enhance the network load-bearing capacity, thereby breaking the trade-off among high strength, creep resistance, and self-healing performance. The resulting TBPI-AFGO1 polymer exhibits excellent thermal stability (Td5% = 349 °C), a high mechanical strength of 103.9 ± 1.11 MPa, the residual strain is only 0.72% after creep recovery at 180 °C. At the same time, after the damage to TBPI-AFGO1 was healed, the mechanical strength of TBPI-AFGO1 recovered to 93.32% of its original value, and the elongation at break recovered to 80.42% of its original value, demonstrating good self-healing capability. Furthermore, integrating TBPI-AFGO1 into carbon fiber fabric endows the fabric with self-healing and recyclability, significantly extending the service life of carbon fiber composites.

Fatigue-induced degradation of mechanical properties remains a major challenge in achieving long-term, reliable service of elastomers. We present a synergistic strategy that couples hydrazone-linked covalent organic framework (H-COF) nanoconfinement with UV-triggered cross-linking to realize self-strengthening poly(urea-urethane) (PUU) elastomers. H-COF nanochannels provide abundant H-bonding sites that immobilize chains and restrict mobility; upon UV irradiation, terminal C = C groups undergo confined radical polymerization within these channels, installing covalent cross-links precisely in highly dynamic regions. This cooperative mechanism strengthens the network while preserving the dissipation of H-bonds, yielding a 3.01× increase in tensile strength (85.1 MPa), a 2.10× enhancement in toughness (327.27 MJ•m- 3), and a 2.20× improvement in fracture energy (303.65 kJ•m- 2). Microstructural analysis reveals reduced domain spacing and homogenized morphology, while digital image correlation demonstrates suppressed strain localization. Moreover, UV irradiation shortens the shape-memory recovery time (Rr up to 99.06%) and intensifies fluorescence, providing a direct optical signal of the recovery process. This work establishes a generalizable design principle for stimuli-programmed self-strengthening under nanoconfinement, advancing elastomers toward adaptive durability.

Polyimides (PIs) are used in cutting-edge engineering fields due to their high mechanical strength, excellent electrical insulation, and low friction coefficient, attributed to their rigid benzene ring structures. However, under prolonged service in harsh environments, PI components are prone to mechanical damage, which substantially increases the risk of operational failure and maintenance costs. Thus, developing self-healing PI materials has become crucial for enhancing operational reliability and extending service life. Nevertheless, achieving a material that simultaneously exhibits high mechanical strength, high healing efficiency, and rapid healing capability remains a formidable challenge. In this work, the formylphenylboronic acid is introduced as a single monomer to concurrently incorporate dynamic imine bonds (-C=N-) and reversible boroxine structures (-B3O3-) into the PI backbone, achieving a "two birds with one stone" molecular design. This strategy endows the resultant PI with excellent mechanical properties (a tensile strength of 87.03 MPa and a break elongation of 21.41%) and a breakthrough self-healing property, enabling repair efficiency of 99.92% and damage repair in just 30 s. Notably, it resolves the critical bottleneck in the field-the typical trade-off between strength/toughness and rapid/healing efficiency-with the achieved efficiency and speed being the highest values reported to date. Furthermore, inspired by the perspiration and healing mechanisms of human skin, a heterogeneous bilayer architecture is constructed to further enhance the healing material's resistance to extreme mechanical damage such as severe abrasion under heavy-load conditions. This work not only opens up a new avenue for designing integrated materials that combine high strength, thermal stability, and ultrafast self-healing capacity, but also provides a practical strategy for prolonging the service life of PIs in extreme environments while mitigating risks associated with unexpected mechanical failures.

The development of wound dressings that promote healing while adapting to complex wound geometries, particularly for inflammation-prone injuries such as diabetic wounds and those occurring at mobile joints, remains a significant challenge. Here, we engineered a 3D printable multifunctional hydrogel adhesive termed PLMATA, fabricated from methacrylate-modified poly-l-lysine and tannic acid (TA). The hydrogel can be printed into customized architectures with high fidelity to adapt to various wound shapes while exhibiting a robust tissue adhesion and mechanical strength. The incorporation of TA enhances hydrogen-bonding interactions, substantially improving both the adhesive and mechanical properties. As a result, the PLMATA hydrogel adheres robustly to skin wounds and remains intact under the dynamic conditions. Furthermore, owing to the inherent nature of PL and TA, the PLMATA hydrogel demonstrates outstanding cytocompatibility, hemocompatibility, and histocompatibility along with potent antioxidant capacity and broad-spectrum antimicrobial efficacy. Murine full-thickness wound models validated significant wound closure acceleration. This work presents printable adaptive hydrogel adhesives that harness enhanced hydrogen-bonding interactions to achieve robust tissue adhesion and mechanical performance while integrating antioxidant and antimicrobial properties, offering a promising strategy for managing diabetic wounds and injuries in mobile joint areas.

Protective coatings are widely used in high-end equipment to isolate external mechanical forces and corrosive environments, thereby safeguarding critical structural materials and extending their service life. Consequently, such coatings are required to combine high adhesion strength, impact resistance, and scratch resistance. These demands are particularly stringent for advanced optical materials. Here, we report a dynamic polyurethane (PU) fabricatedby integrating hierarchical hydrogen bonds (HB) and thiourethane dynamic bonds. The synergistic effect of these dynamic bonds enables the resulting PU-IS with enhanced interfacial adhesion and energy dissipation, leading to a balanced combination of mechanical strength, toughness, strong yet on-demand detachable adhesion, self-healing, and recyclability. Notably, the designed PU-IS exhibits outstanding tensile strength (63.7  MPa), exceptional toughness (110.96  MJ·m−3), strong adhesion (7.11  MPa), excellent thermal stability, and high optical transparency (>85%), as well as impact resistance, scratch resistance, fatigue resistance, and long‑term durability. These combined attributes make PU‑IS a promising candidate for advanced protective coatings, especially for optical applications. This work not only establishes a versatile design paradigm for high-performance protective coatings but also significantly expands the application potential of polyurethanes in advanced protective technologies.

Inspired by collagen fibers and elastin in biological systems, this study developed a novel dual-network intelligent protective material (TPU-CANs-M) by integrating a dynamic reversible network (containing hierarchical hydrogen bonds and boron-oxygen bonds) with a stable thermoplastic polyurethane (TPU) chemical cross-linking network, effectively solving the technical limitations of conventional shear-thickening materials such as low stability and fluidic nature. The energy dissipation mechanism mainly originates from the reversible breakage and reformation of hierarchical hydrogen bonds and dynamic boron-oxygen bonds. Notably, the incorporation of the reversible dynamic network (CANs-M) enables precise regulation of the microphase separation, imparting outstanding properties, including a tensile strength of 20.85 MPa, a fracture elongation of 1283%, a toughness of 154.42 MJ m-3, and a self-healing efficiency of 81%. Furthermore, impact tests demonstrate that the material exhibits a 20% reduction in peak impact force compared to TPU and shows significant strain rate sensitivity, demonstrating outstanding strain-rate sensitivity and buffering performance. This research provides innovative strategy for developing advanced protective materials that combine high strength, superior toughness, and selfhealing capabilities.

The conflict between the high performance and non-recyclability of thermosetting plastics poses a major sustainability challenge, particularly for high-value materials like polyimide. By employing vanillin- and glycerolderived crosslinkers connected via dynamic imine bonds, a dual-function bio-crosslinked recyclable polyimide has been developed. This material combines strong adhesion (21.87 MPa), lubricating properties, and closedloop recyclability. It exhibits a tensile strength exceeding 112.22 MPa with an elongation at break of 14.86 %. A key feature is its ability to undergo complete depolymerization and be reformed under mild, catalyst-free conditions using a single solvent (DMF). Notably, after thermal compression recycling, its tensile strength increased by 11.77 % to 125.43 MPa, and its Young's modulus significantly improved by 47.60 % to 3.69 GPa. Furthermore, its composite with 8 % multi-walled carbon nanotubes (MWCNTs) demonstrated significantly enhanced tribological performance, achieving a friction coefficient of 0.1022 and a wear rate reaching 0.0512 & times; 10-5 mm3 center dot N-1 center dot m-1. This represents reductions of 79.20 % and 98.63 %, respectively, compared to neat PI. This research establishes a new paradigm for recyclable, high-performance thermosetting materials, offering a sustainable material solution for applications such as seals, bearings, and flexible electronics.

Poly(ether-ether-ketone) (PEEK) is widely used in aerospace applications as a self-lubricating material owing to its exceptional mechanical strength and thermal stability. Although fused deposition modeling (FDM) 3D printing is commonly employed for PEEK fabrication, the precise printing of complex and intricate structures remains challenging. In this study, we developed a novel 3D printing strategy for the precise molding of high-performance PEEK using digital light processing (DLP) to print a photocurable resin, in which ACMO-PEGDA (PACMO) was blended with commercial PEEK powder. In the photocured structure, PEEK powder was confined within the elastic crosslinking network. Each 3D printed PEEK sample underwent individual phase transitions in response to temperature changes. Experimental results confirmed an exceptional shape memory performance, with shape fixation and recovery ratios exceeding 94%. The 4D printed PEEK components exhibited high strength and facilitated the transition from 2D to 3D complex structures. Furthermore, the fabricated components demonstrated an exceptionally low coefficient of friction of below 0.1, offering a groundbreaking solution for customized production of advanced wear-resistant mechanical components. This study represents a significant advancement in PEEK processing technology, establishes new paradigms for high-performance PEEK 3D/4D printing, and opens new avenues for the development of next-generation intelligent devices with enhanced performance.

To address the demand for lightweight, wear-resistant PEEK friction materials in humanoid robotics, this study employed liquid-assisted mechanochemical synthesis to create ZIF-62 crystals. These crystals were then incorporated as functional fillers into PEEK to fabricate ZIF-62/PEEK composites using fused deposition modeling (FDM) technology. The analysis explored how the material's properties related to mechanics and wear are affected by the amount of ZIF-62 (1-3 wt.%), utilizing pin-on-ring friction tests with GCr15 steel rings as the counterface. The tribological mechanisms of the composites were explored by analyzing the morphology of the composites' surfaces after wear, along with the morphology and chemical composition of the transfer films developed on the matching surface. Particular emphasis was placed on the impact of interfacial tribochemical reactions and transfer film establishment on the composite's tribological performance. Research indicates that the integration of ZIF-62 boosts the composite's strength and ability to withstand wear. Specifically, at a ZIF-62 concentration of 3 wt.%, the composites reach 3.7 x 10-6 mm3/Nm, representing a 71.5% decline compared to pure PEEK, showcasing outstanding anti-wear capabilities. Findings of the study provide a unique solution for the tribological modification of PEEK, which is instructive for the design and preparation of PEEK tribo-materials used in humanoid robots.

4D printing enables the creation of materials with precision architectures that evolve in shape or function over time, holding significant potential in fields like soft robotics and biomedical devices. However, achieving spatiotemporally controlled, high-performance multi-material systems remains challenging. Here, we introduce a strategy for the spatiotemporally controlled 4D printing of high-strength poly(urethane-urea) elastomers via topological reconfiguration. This is achieved by incorporating a side-chain carbamate monomer 2-(((3,3-dime-thylbutoxy(carbonyl)amino)ethyl methacrylate (DMB) and a photo-responsive extender p-benzoquinone dioxime (BQDO), which was introduced through hindered urea bond, it simultaneously enhances printability and introduces near-infrared (NIR) responsiveness. The post heating treatment significantly enhanced the mechanical performance of PUUB, increasing the tensile strength from 16.7 f 0.4 MPa to 27.0 f 1.3 MPa, and the toughness from 31.4 f 1.1 MJ/m3 to 72.4 f 4.4 MJ/m3. Additionally, it exhibited excellent shape memory performance, with a shape fixity ratio of 98.46% and a shape recovery ratio of 92.17%. Critically, the photothermal-triggered topological reconfiguration allows for remote, selective modulation of material properties after printing, enabling spatiotemporal control over the final performance. By incorporating a photothermal compound into the polymer, dynamic bond exchange remains inactive under UV irradiation during DLP printing but can be remotely and locally activated by NIR light. This enables spatially selective property programming, and the photo-thermally responsive regions further allow multi-responsive shape memory behavior for spatiotemporal actuation. This work represents a new paradigm for creating versatile, high-performance multi-material 4D systems for advanced applications.

Clear aligners have become a preferred orthodontic solution due to their aesthetics, comfort, and convenience. However, current aligners still suffer from poor fit caused by thermoforming-induced dimensional inaccuracies and force mismatch due to stress relaxation in thermoplastic materials. Here we address these limitations by developing a biocompatible, highly transparent polyurethane-based material (PUP) tailored for high-precision DLP printing. The PUP ink enables rapid, spatially resolved curing within 30 s and supports high-fidelity printing with feature sizes down to similar to 10 mu m. Moreover, 4D-printed PUP aligners combine accurate fit with programmable, long-term force delivery and can be reshaped for multiple treatment stages. Notably, the representative formulation meets clear-aligner-relevant yield thresholds (yield strength > 25 MPa and yield strain > 4%), supporting stable elastic force output within a clinically meaningful deformation window. This work demonstrates a smart aligner strategy that integrates precision manufacturing with active force control through shape memory, offering a practical route toward next-generation personalized orthodontic devices. [GRAPHICS]

With the global surge in polymeric material consumption, the exploitation of sustainable thermosetting composites with high mechanical performance, superior tribological properties and recyclability is urgently demanded. In this study, we synthesized a bio-based cross-linked polyimide (Bio-PIx) via Schiff base reaction, and the prepared materials exhibit high thermomechanical properties, with a tensile strength of approximately 105.6 MPa and a Young's modulus of about 3.5 GPa. Moreover, it possesses recyclability, as evidenced by a monomer recovery rate of up to 90% under mild conditions through the cleavage and recombination of imine bonds (-C=N-). Furthermore, reduced graphene oxide (rGO) was selected as a solid lubricant to fabricate rGO-reinforced Bio-PIx (rGO@Bio-PIx) composites. Results demonstrated that compared with pure Bio-PIx, the rGO@Bio-PIx composites not only maintained favorable mechanical stability but also exhibited significantly enhanced tribological properties with a 65.6% and 55.5% reduction in friction coefficient (COF) and volume wear rate (W), respectively. More importantly, rGO@Bio-PIx can be depolymerized into monomers at room temperature, achieving a 95% recovery rate for rGO. Notably, the rGO@Bio-PIx composite material can be reconstructed without requiring catalysts, and the recycled rGO@Bio-PIx (R-rGO@Bio-PIx) retained its superior performance, demonstrating renewable lubricating property. This approach presents a promising pathway for developing high-performance thermoset polyimide composites for sustainable multifunctional applications.

Carbon fibers were functionalized by metal-organic frameworks (MOFs), referred to as MCFs, through chemical self-polymerization and solvothermal reactions, and then combined with polytetrafluoroethylene (PTFE) to construct a hard-soft cross-scale synergistic structure, resulting in the preparation of polyimide (PI) composite coatings. Tribological tests were conducted under different conditions, after which the fundamental role of MCFs and PTFE in modifying the friction-reduction and anti-wear performance of PI was discussed based on in-depth characterization of the composite coatings' worn surface and transfer films formed on the counter steel surface. It was revealed that the MCFs/15PT/PI composite coating exhibited excellent tribological properties, which also exhibited high friction stability and wear resistance across varying loads and sliding speeds. Additionally, the composite coating was found to be potentially applicable for maintenance-free applications due to its excellent long-term tribological performance.

Due to their unique organic-inorganic hybrid structures, metal-organic frameworks (MOFs) have shown increasing potential as fillers for polymer self-lubricating composites. In this study, a systematic investigation of three structurally different MOFs (ZIF-8, MOF-5, and UiO-66, each at 3 wt%) in polyimide (PI) composite coatings revealed that their incorporation enhanced the mechanical properties. Notably, UiO-66 exhibited the most pronounced reinforcement, attributable to its strong interfacial bonding with the resin matrix, which led to an 18.4% increase in tensile strength as well as corresponding enhancements in elastic modulus and hardness. To gain insight into the friction and wear mechanisms of MOFs/PI composite coatings, ball-on-disc tests were complemented by molecular dynamics (MD) simulations and density functional theory (DFT) calculations. This combined approach elucidated the role of MOFs at the frictional contact interface and their influence on transfer film formation. The conclusions regarding the intrinsic relationship between the structure of MOFs and their tribological mechanisms are of both theoretical and practical importance for developing PI composite coatings for self-lubricating bushings, bearing shells and sliders.

The development of high-performance polymer composites—combining strength, low friction, and wear resistance—remains an industrial challenge. In the present study, zeolite imidazolate framework ZIF-62 served as a multifunctional filler to fabricate ZIF-62/PEEK composites via fused deposition modeling (FDM). The effects of ZIF-62 on PEEK’s friction and wear were systematically investigated. By modulating the Im/BIm molar ratio in ZIF-62, we controlled the kinetics and composition of interfacial transfer film formation during sliding, thereby enhancing PEEK’s tribological performance. The optimal composition (ZIF-62/PEEK with Zn:Im:BIm = 1:1.5:0.5) reduced PEEK’s wear rate by 90 % to 1.45 × 10⁻⁶ mm3/Nm under 4 MPa × 0.25 m/s. The mechanisms behind this improvement were discussed based on multiscale characterization and molecular dynamics simulations. It was revealed that Zn species were released through the breakage of Zn–N bonds and reacted with degraded PEEK to form ZnO, while simultaneously inducing tribo-catalyzed graphitization. These products combined with iron oxides from the counterface to form a robust transfer film. This work establishes ligand engineering as a strategy for designing next-generation PEEK tribomaterials.

Friction and wear induced energy dissipation and equipment failure represent pervasive challenges in engineering. Conventional lubricating materials, constrained by limited functionality, susceptibility to degradation, and poor maintainability, are often inadequate...

Polyimide (PI), a special engineering plastic, features robust mechanical properties and exceptional thermal stability. However, its processing and molding are limited by thermal pressing, making the fabrication of high performance customized complex 3D shapes a significant challenge. Here, we present a PI combines high performance with the ability to access 3D printing and recyclability, facilitated by a snap-hook polyimide (SHPI) strategy based on dynamic boroxine network. Capping the liner PI with phenylboronic acid, which could reversible formation of six-membered boroxine rings occurs at both ends of the liner PI under heat and specific solvents, resulting in dynamic crosslinked PI (DCPI) and liner SHPI. Due to the stability and high bond energy of the boroxine, DCPI exhibits exceptional mechanical properties (tensile strength ti 110 MPa, Young's modulus ti 3 GPa) and thermal performance (Tg ti 223 degrees C, Td ti 539 degrees C). The selective cleavage of boroxine bonds enables the snap-hook functionality that allows reversible conversion between DCPI and SHPI, imparting solubility and facilitating infinite recyclability, 3D printability, and sustainable printability, thereby achieving the creation and elimination of high-performance PI 3D structures. Moreover, the 3D-printed PI sealing ring structure, as a demonstration, showcases its limitless potential for applications in the aerospace industry. This work opens new avenues for the personalized construction of high-performance engineering polymers and provides a viable approach for the development of sustainable 3D printing.

To enhance the mechanical properties of polyurethane elastomers, various strategies have been developed, including the incorporation of multiple hydrogen bonds, mechanical interlocking, and supramolecular interactions. However, achieving an optimal balance between strength and toughness while maintaining high tensile properties at both room and cryogenic temperatures remains a significant challenge. In this study, we synthesized a poly(boron-urethane) with ultra-high performance by introducing aromatic side chains into the polyurethane matrix. The resulting poly(boron-urethane) demonstrates remarkable mechanical properties, with tensile strength (70.1 +/- 4.4 MPa) and fracture toughness (437.5 +/- 61.1 MJ/m3). These exceptional mechanical properties were attributed to the synergistic effects of pi-pi stacking interactions and hierarchical hydrogen bonding. This synergy not only serves as reversible cross-linking points and sacrificial bonds that facilitate substantial energy dissipation, but also forms nanostructured domains that act as nanofillers, thereby enhancing the mechanical properties. Furthermore, the incorporation of bulky aromatic rings of the chain extenders mitigate the crystallization tendency of PTMEG, resulting in improved low-temperature flexibility. This chemcial modification contributes to significant tensile strength (100.6 MPa) and fracture toughness (237.5 MJ/m3) at -40 degrees C, along with excellent solvent resistance. Overall, the combination of pi-pi stacking and hierarchical hydrogen bonding, synergistically enhances the entropic elasticity of the elastomer network, effectively balancing the strength and toughness of the material across varying temperatures, making it well-suited for extremely cold environments.