Xuzhou Yan

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 …

Constructing an artificial solid electrolyte interphase (ASEI) on Li metal anodes (LMAs) is a potential strategy for addressing the dendrite issues. However, the mechanical fatigue of the ASEI caused by stress accumulation under the repeated deformation from the Li plating/stripping is not taken seriously. Herein, we introduce a mechanically interlocked [an]daisy chain network (DCMIN) into the ASEI to stabilize the Li metal/ASEI interface by combining the functions of energy dissipation and fast Li‐ion transport. The DCMIN featured by large‐range molecular motions was cross‐linked via efficient thiol‐ene click chemistry; thus, the DCMIN has flexibility and excellent mechanical properties. As an ASEI, the crown ether units in DCMIN not only interact with the dialkylammonium of a flexible chain, forming the energy dissipation behavior but also coordinate with Li ion to support the fast Li‐ion transport in DCMIN …

Foldamer is a scaled‐down version of coil spring, which can absorb and release energy by conformational change. Here, polymer networks with high‐density of molecular springs were developed by employing anion‐coordination‐based foldamers as the monomer. The coiling of the foldamer is controlled by oligourea ligands coordinating to chloride ions; subsequently, the folding and unfolding of foldamer conformations endow the polymer network with excellent energy dissipation and toughness. The mechanical performance of the corresponding polymer network shows a dramatic increase from P‐L2UCl (non‐folding), P‐L4UCl (a full turn) to P‐L6UCl (1.5 turns), in terms of strength (2.62 MPa; 14.26 Mpa; 22.93 Mpa), elongation at break (70%; 325%; 352%), Young’s modulus (2.69 MPa; 63.61 Mpa; 141.50 Mpa), and toughness (1.12 MJ/m3; 21.39 MJ/m3; 49.62 MJ/m3), respectively, which are also better than …

Inspired by the drawstring structure in daily life, here we report the development of a drawstring‐mimetic supramolecular complex at the molecular scale. This complex consists of a rigid figure‐of‐eight macrocyclic host molecule and a flexible linear guest molecule which could interact through three‐point non‐covalent binding to form a highly selective and efficient host‐guest assembly. The complex not only resembles the drawstring structure, but also mimics the properties of a drawstring with regard to deformations under external forces. The supramolecular drawstring can be utilized as an interlocked crosslinker for poly(methyl acrylate), and the corresponding polymer samples exhibit comprehensive enhancement of macroscopic mechanical performance including stiffness, strength, and toughness.

Covalent adaptable networks (CANs), comprising polymer networks crosslinked by dynamic covalent bonds (DCBs), have garnered considerable attention as sustainable materials. Mastering the stress relaxation of CANs is essential for controlling their viscoelastic properties. An unexpected acceleration of stress relaxation has been observed in CANs containing dual dynamic bonds. The dynamic behavior of the second dynamic bonds can accelerate stress relaxation and lower the relaxation activation energy of dual dynamic CANs compared to analogous CANs that rely on only one type of DCB. These findings complement current approaches that utilize catalysts or adjust network parameters. In this minireview, we summarize the synergistic acceleration effects in various CANs containing dual dynamic bonds. We classify these effects based on the second dynamic bonds, including noncovalent bonds …

Loops are prevalent topological structures in cross‐linked polymer networks, resulting from the folding of polymer chains back onto themselves. Traditionally, they have been considered as defects that compromise the mechanical properties of the network, leading to extensive efforts in synthesis to prevent their formation. In this study, we introduce the inclusion of cyclic dibenzo‐24‐crown‐8 (DB24C8) moieties within the polymer network strands to form CCNs, and surprisingly, these loops enhance the mechanical performances of the network, leading to tough elastomers. The toughening effect can be attributed to the unique cyclic structure of DB24C8. The relatively small size and the presence of rigid phenyl rings provide the loops with relatively stable conformations, allowing for substantial energy dissipation upon the application of force. Furthermore, the DB24C8 rings possess a broad range of potential …

Comprehensive Summary Traditional carbon fiber‐reinforced polymers based on thermoset matrix have been extensively used in the fields of wind turbine blades, automotive sector, and aerospace, among many others. However, there is still a major challenge of recycling those polymers due to the high cost and adverse impacts on the environment. In this work, we apply a polyimine network as matrix, which possess considerable tensile and thermal properties, to prepare the carbon fiber reinforced polyimine materials with trifluoromethyl diphenoxybenzene units (CFRFP) using a prepreg‐based compression molding method. The CFRFP can be reshaped or reprocessed by heat or with water rapidly, and exhibited multifunction, including welding, chemical recycling, etc. These unique findings gained from our study will facilitate the manufacturing capability and enrich the types of fiber‐reinforced composites.

ConspectusMechanically interlocked polymers (MIPs) such as polyrotaxanes and polycatenanes are polymer architectures that incorporate mechanical bonds, which represent a compelling frontier in polymer science. MIPs with cross-linked structures are known as mechanically interlocked networks (MINs) and are widely utilized in materials science. Leveraging the motion of mechanical bonds, MINs hold the potential for achieving a combination of robustness and dynamicity. Currently, the reported MINs predominantly consist of networks with discrete mechanical bonds as cross-linking points, exemplified by well-known slide-ring materials and rotaxane/catenane cross-linked polymers. The motion of these mechanically interlocked cross-linking points facilitates the redistribution of tension throughout the network, effectively preventing stress concentration and thereby enhancing material toughness. In these …

Antibiotics are among the most used weapons in fighting microbial infections and have greatly improved the quality of human life. However, bacteria can eventually evolve to exhibit antibiotic resistance to almost all prescribed antibiotic drugs. Photodynamic therapy (PDT) develops little antibiotic resistance and has become a promising strategy in fighting bacterial infection. To augment the killing effect of PDT, the conventional strategy is introducing excess ROS in various ways, such as applying high light doses, high photosensitizer concentrations, and exogenous oxygen. In this study, we report a metallacage-based PDT strategy that minimizes the use of ROS by jointly using gallium-metal organic framework rods to inhibit the production of bacterial endogenous NO, amplify ROS stress, and enhance the killing effect. The augmented bactericidal effect was demonstrated both in vitro and in vivo. This proposed …

Supramolecular polymer networks(SPNs) have gained increasing research attention due to their reversible and tunable nature in the preparation of adaptive materials. The use of hierarchical self-assembly techniques is an emerging strategy for the fabrication of smart supramolecular polymer networks, but corresponding study is still rare. Herein, we have reported a novel supramolecular polymer network through complementary host-guest interactions and phototriggered quadruple H-bonding cross-linking. Specifically, we design and synthesize an H1G1-type monomer consisting of a benzo-21-crown-7(B21C7) host(H1), a dialkylammonium salt guest(G1) and a photolabile o-nitrobenzyl ether protected ureidopyrimidinone(Upy) moiety. B21C7 and ammonium moieties can first form a linear supramolecular polymer through complementary host-guest interactions. Under photoirradiation, the Upy groups on the SP …

Dynamic covalent chemistry opens up great opportunities for a sustainable society by producing reprocessable networks of polymers and even thermosets. However, achieving the closed‐loop recycling of polymers with high performance remains a grand challenge. The introduction of aromatic monomers and fluorine into covalent adaptable networks is an attractive method to tackle this challenge. Therefore, we present a facile and universal strategy to focus on the design and applications of polyimine vitrimers containing trifluoromethyl diphenoxybenzene backbones in applications of dynamic covalent polymers. In this study, fluorine‐containing polyimine vitrimer networks (FPIVs) were fabricated, and the results revealed that the FPIVs not only exhibited good self‐healability, malleability and processability without the aid of any catalyst, but also possessed decent mechanical strength, superior toughness and …

Supramolecular polymer networks (SPNs) have attracted much research attention due to their good performance in the preparation of adaptive materials. Controlling the distribution of supramolecular interactions in the networks is a good strategy to tune the properties of SPNs, but corresponding study is still rare. Herein, we construct two triblock copolymers in ABA and BAB forms to control the supramolecular interaction concentrated in A block, leading to two SPNs with divergent mechanical performances. In specific, the SPN‐1 formed by ABA triblock copolymer displays a slightly and densely distributed hard domain and a compact network, resulting in a decent toughness. While the SPN‐2 composed of BAB triblock copolymer is rigid and less elastic, whose microphase‐separated structures are more obvious, making the network difficult to withstand larger strains. These findings are conducive to deepening the …

Simultaneously introducing covalent and supramolecular cross‐links into one system to construct dually cross‐linked networks, has been proved an effective approach to prepare high‐performance materials. However, so far, features and advantages of dually cross‐linked networks compared with those possessing individual covalent or supramolecular cross‐linking points are rarely investigated. Herein, on the basis of comparison between supramolecular polymer network (SPN), covalent polymer network (CPN) and dually cross‐linked polymer network (DPN), we reveal that the dual cross‐linking strategy can endow the DPN with integrated advantages of CPN and SPN. Benefiting from the energy dissipative ability along with the dissociation of host–guest complexes, the DPN shows excellent toughness and ductility similar to the SPN. Meanwhile, the elasticity of covalent cross‐links in the DPN could rise the …

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and …

Artificial skin that simultaneously mimics sensory feedback and mechanical properties of natural skin holds substantial promise for next-generation robotic and medical devices. However, achieving such a biomimetic system that can seamlessly integrate with the human body remains a challenge. Through rational design and engineering of material properties, device structures, and system architectures, we realized a monolithic soft prosthetic electronic skin (e-skin). It is capable of multimodal perception, neuromorphic pulse-train signal generation, and closed-loop actuation. With a trilayer, high-permittivity elastomeric dielectric, we achieved a low subthreshold swing comparable to that of polycrystalline silicon transistors, a low operation voltage, low power consumption, and medium-scale circuit integration complexity for stretchable organic devices. Our e-skin mimics the biological sensorimotor loop, whereby a …

Mechanical bonds have been utilized as promising motifs to construct mechanically interlocked aerogels (MIAs) with mechanical adaptivity and multifunctionality. However, fabricating such aerogels with not only precise chemical structures but also dynamic features remains challenging. Herein, we present MIAs carrying dense [2]rotaxane units, which bestow both the stability and flexibility of the aerogel network. Owing to the stable chemical structure of a [2]rotaxane, MIAs possessing a precise and full‐scale mechanically interlocked network could be fabricated with the aid of diverse solvents. In addition, the dynamic nature of the [2]rotaxane resulted in morphologies and mechanical performances of the MIAs that can be dramatically modulated under chemical stimuli. We hope that the structure–property relationship in MIAs will facilitate the development of mechanically interlocked materials and provide novel …

Stretchable hybrid devices have enabled high-fidelity implantable, – and on-skin, – monitoring of physiological signals. These devices typically contain soft modules that match the mechanical requirements in humans, and soft robots,, rigid modules containing Si-based microelectronics, and protective encapsulation modules,. To make such a system mechanically compliant, the interconnects between the modules need to tolerate stress concentration that may limit their stretching and ultimately cause debonding failure, –. Here, we report a universal interface that can reliably connect soft, rigid and encapsulation modules together to form robust and highly stretchable devices in a plug-and-play manner. The interface, consisting of interpenetrating polymer and metal nanostructures, connects modules by simply pressing without using pastes. Its formation is depicted by a biphasic network growth model. Soft–soft …

Mechanically interlocked polymers (MIPs) are capable of synchronously directing force and motion empowered by collective mechanical bonds, thus constituting a versatile platform for developing advanced polymer materials. However, it is still a significant challenge to facilely prepare structurally complicated MIPs. Herein, we describe a supramolecular polymerization followed by an interlocking strategy to construct [an]daisy chain-based MIPs, namely, mechanically interlocked [an]daisy chain networks (DCMINs). On account of the linkage of continuous mechanical bonds, the cyclic components on the [an]daisy chain backbones of DCMINs are capable of undergoing a synergistic inward movement under external force and thus maximizing the contractile motion, which represents an unexploited motional way. The synchronous motions of coherent [an]daisy chains could be readily activated to adapt to the network …

Supramolecular polymer networks (SPNs) demonstrate great potential in the development of smart materials owing to their attractive dynamic properties. However, as they suffer from the inherent weak bonding of most noncovalent cross‐links, it remains a significant challenge to construct SPNs with outstanding mechanical performance. Herein, we exploit the cryptand/paraquat host‐guest recognition motifs as cross‐links to prepare a class of highly strong and tough SPNs. Unlike those supramolecular cross‐links with relatively weak binding abilities, the cryptand‐based host‐guest interactions have a high association constant and steady complexing structure, which effectively stabilizes the network and resists mechanical deformation under external force. Such favorable structural stability endows our SPNs with greatly enhanced mechanical performance, compared with the control‐1 cross‐linked by the weakly …

The separator with high Young’s modulus can avoid the danger of large-sized dendrites, but regulating the chemical behavior of lithium (Li) at the separator/anode interface can effectively eliminate the dendrite issue. Herein, a polyimine aerogel (PIA) with accurate nitrogen (N) functional design is used as the functional separator in Li metal batteries to promote uniform Li nucleation and suppress the dendrite growth. Specifically, the imine (N1) and protonated tertiary amine (N2) sites in the molecular structure of the PIA are significantly different in electron cloud density (ECD) distribution. The N1 site with higher ECD and the N2 site with lower ECD tend to attract and repulse Li+ through electrostatic interactions, respectively. This synergy effect of the PIA separator accelerates the interfacial Li+ diffusion on the Li anode to sustain a uniform two-dimensional Li nucleation behavior. Meanwhile, the well-defined …