Mobility Control of Mechanical Bonds to Modulate Energy Dissipation in Mechanically Interlocked Networks.

Mechanically interlocked networks (MINs) with dense mechanical bonds can amplify the dynamic behaviors of the mechanical bonds to exhibit decent mechanical properties. Energy dissipation resulting from mechanical bond motion is essential for improving toughness, yet effective strategies to optimize this process remain underexplored. Here, by designing mechanical bond models with controllable mobility, we establish a fortification strategy for the two key factors governing energy dissipation, host-guest recognition and sliding friction, thereby enabling mechanical property enhancement of mechanically interlocked materials.

Stretchable [2]rotaxane-bridged MXene films applicable for electroluminescent devices.

Titanium carbide (TiCT) MXene has prominent mechanical properties and electrical conductivity. However, fabricating high-performance macroscopic films is challenging, as weak interlayer interactions limit their mechanical performance. Here, we introduce [2]rotaxane, a mechanically interlocked molecule, to enhance MXene films.

Molecularly Woven Polymer Aerogels.

Aerogels with abundant nanopores and large specific surface areas have extensive potential in various applications but are constrained by fragility and difficulty in degradation. Currently, the exploration of adaptive and reprocessing aerogels has become increasingly urgent, as the demand for intelligent and sustainable materials intensifies. Here, we present a molecular weaving strategy to construct molecularly woven polymer aerogels (WPAs) via catalyst-free aldimine condensation between prewoven aldehyde-functionalized Cu(I) bisphenanthroline (Cu(PBD)) and flexible 4,4'-diaminodibenzyl (DB).

Ring-Toughened Polymer Networks: The Mighty Impact of Specially Designed Rings on Mechanical Properties.

Polymer network materials are gaining significance in daily life and industrial applications. Improving polymer network materials' mechanical properties has long been a focus for chemists and materials scientists. Generally, rings in networks are viewed as adverse elements leading to reduced mechanical performance.

Molecular Origin of the Stretchability and Fatigue-Resistance of Rotaxane-Based Mechanically Interlocked Polymer Networks.

Rotaxane-based polymer networks leveraging host-guest recognition have recently emerged as a versatile platform for developing smart materials. Despite numerous studies on these polymers, their unique mechanical properties are mostly associated with the sliding motion of the macrocycle along the axle, leaving the impact of the presence or absence of interlocked structures on the mechanical performance of materials yet to be directly demonstrated. In this work, we present a densely (pseudo)rotaxane-based supramolecular polymeric network (SPN) and a mechanically interlocked network (MIN) as model systems to explore how the mechanical interlocking unit dominates the material properties.

Light-Induced Transformation from Covalent to Supramolecular Polymer Networks.

Stimuli-responsive polymers have demonstrated significant potential in the development of smart materials due to their capacity to undergo targeted property changes in response to external physical or chemical stimuli. However, the scales of response in most existing stimuli-responsive polymer systems are mainly focused on three levels: functional units, chain conformations, or polymer topologies. Herein, we have developed a covalent polymer network (CPN) capable of converting into a supramolecular polymer network (SPN) within bulk materials directly at the scale of polymer network types.

Robust Mechanically Interlocked Network Ionogels.

Ionogels have attracted considerable attention as versatile materials due to their unique ionic conductivity and thermal stability. However, relatively weak mechanical performance of many existing ionogels has hindered their broader application. Herein, we develop robust, tough, and impact-resistant mechanically interlocked network ionogels (MINs) by incorporating ion liquids with mechanical bonds that can dissipate energy while maintain structural stability.

Covalent Adaptable Poly[2]rotaxane Networks via Dynamic C-N Bond Transalkylation.

Covalent adaptable networks (CANs), a novel class of crosslinked polymers with dynamic covalent bonds, have gained significant attention for combining the durability of thermosets with the reprocessability of thermoplastics, making them promising for emerging applications. Here, we report the first example of poly[2]rotaxane-type covalent adaptable networks (CANs), in which oligo[2]rotaxane backbones characterized by densely packed mechanical bonds, are cross-linked through dynamic C-N bonds. The oligo[2]rotaxane backbones could guarantee the mechanical properties of the CANs.

Durable and Damageless Supramolecular Binder for Fast, Stable, and Sustainable Si-Based Anodes.

Mechanical fatigue of the binders during the repeated volume change of Si-based anodes induces binder network collapse, resulting in lithium-ion batteries (LIBs) failing prematurely. Herein, we designed a damageless polymer binder with a mechanically interlocked network utilizing [n]daisy chains (MIN) and poly(acrylic acid) (PAA) to improve the structural cohesion of the Si-based anode. This MIN@PAA binder exhibits robust mechanical properties, high elasticity, and excellent adhesion.

Energy Dissipation and Toughening of Covalent Networks via a Sacrificial Conformation Approach.

Covalent polymer networks find wide utility in diverse engineering applications owing to their desirable stiffness and resilience. However, the rigid covalent chemical structure between crosslinking points imposes limitations on enhancing their toughness. Although the incorporation of sacrificial chemical bonds has shown promise in improving toughness through energy dissipation, composite networks struggle to maintain both rapid recovery and stiffness.

Colloid Electrolyte Containing LiP Nanoparticles for Highly Stable 4.7 V Lithium Metal Batteries.

Lithium metal batteries (LMBs) with LiNiCoMnO (NCM811) cathodes have garnered significant interest as next-generation energy storage devices due to their high energy density. However, the instability of their electrode/electrolyte interfaces in regular carbonate electrolytes (RCEs) results in a rapid capacity decay. To address this, a colloid electrolyte consisting of LiP nanoparticles uniformly dispersed in the RCE is developed by a one-step synthesis.

Mechanically Interlocked [an]Daisy Chain Adhesives with Simultaneously Enhanced Interfacial Adhesion and Cohesion.

Adhesives have been widely used to splice and repair materials to meet practical needs of humanity for thousands of years. However, developing robust adhesives with balanced adhesive and cohesive properties still remains a challenging task. Herein, we report the design and preparation of a robust mechanically interlocked [an]daisy chain network (MIN) adhesive by orthogonal integration of mechanical bonds and 2-ureido-4[1H]-pyrimidone (UPy) H-bonding in a single system.

Dynamically Cross-linked Oligo[2]rotaxane Networks Mediated by Metal-Coordination.

Polyrotaxanes (PRs) have attracted significant research attention due to their unique topological structures and high degrees of conformational freedom. Herein, we take advantage of an oligo[2]rotaxane to construct a novel class of dynamically cross-linked rotaxane network (DCRN) mediated by metal-coordination. The oligo[2]rotaxane skeleton offers several distinct advantages: In addition to retaining the merits of traditional polymer backbones, the ordered intramolecular motion of the [2]rotaxane motifs introduced dangling chains into the network, thereby enhancing the stretchability of the DCRN.

Stimuli-responsive mechanically interlocked polymer wrinkles.

Artificial wrinkles, especially those with responsive erasure/regeneration behaviors have gained extensive interest due to their potential in smart applications. However, current wrinkle modulation methods primarily rely on network rearrangement, causing bottlenecks in in situ wrinkle regeneration. Herein, we report a dually cross-linked network wherein [2]rotaxane cross-link can dissipate stress within the wrinkles through its sliding motion without disrupting the network, and quadruple H-bonding cross-link comparatively highlight the advantages of [2]rotaxane modulation.

Mechanically Interlocked Polyrotaxane Networks with Collective Motions of Multiple Main-Chain Mechanical Bonds.

Type I main-chain polyrotaxanes (PRs) with multiple wheels threaded onto the axle are widely employed to design slide-ring materials. However, Type II main-chain PRs with axles threading into the macrocycles on the polymer backbones have rarely been studied, although they feature special topological structures and dynamic characteristics. Herein, we report the design and preparation of Type II main-chain PR-based mechanically interlocked networks (MINs), based on which the relationship between microscopic motion of mechanical bonds on the PRs and macroscopic mechanical performance of materials has been revealed.

Development of Fluorenyl-Based Copolyimines with Adjustable Mechanical Properties, Recyclability and Friction Resistance.

Dynamic polyimines are a class of fascinating dynamic polymers with recyclability and reparability owing to their reversible Schiff-base reactions. However, balancing the dynamic properties and mechanical strength of dynamic polyimines presents a major challenge due to the dissociative and associative nature of the imine bonds. Herein, we introduced bulky fluorene groups and polyether amine into the skeleton of polyimine networks to achieve a tradeoff in comprehensive properties.

A Stretchable and Tough Graphene Film Enabled by Mechanical Bond.

The pursuit of fabricating high-performance graphene films has aroused considerable attention due to their potential for practical applications. However, developing both stretchable and tough graphene films remains a formidable challenge. To address this issue, we herein introduce mechanical bond to comprehensively improve the mechanical properties of graphene films, utilizing [2]rotaxane as the bridging unit.

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.

Anion-Coordination Foldamer-Based Polymer Network: from Molecular Spring to Elastomer.

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 oligo(urea) ligands coordinating to chloride ions; subsequently, the folding and unfolding of foldamer conformations endow the polymer network with excellent energy dissipation and toughness.

A Crown-Ether-Based Elastomer Bearing Loop Structures with Dissipating Characteristics and Enhanced Mechanical Performance.

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.

Mechanically Interlocked Polymers with Dense Mechanical Bonds.

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.

Mechanically Interlocked Interphase with Energy Dissipation and Fast Li-Ion Transport for High-Capacity Lithium Metal Batteries.

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, this work introduces a mechanically interlocked [an]daisy chain network (MIN) into the ASEI to stabilize the Li metal/ASEI interface by combining the functions of energy dissipation and fast Li-ion transport.

Assembly and Utility of a Drawstring-Mimetic Supramolecular Complex.

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.

A polyimine aerogel separator with electron cloud design to boost Li-ion transport for stable Li metal batteries.

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.

Mechanically Interlocked [2]Rotaxane Aerogels with Tunable Morphologies and Mechanical Properties.

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.