Xuzhou Yan

Muscle integrates molecular-machine motion with hierarchical structural organization, enabling it to sustain large deformations under physiological loads. Mechanically interlocked molecules offer a versatile platform to mimic such molecular-level motion, but efficiently translating it into macroscopic material performance, akin to muscle, remains challenging. Herein, we report a mechanically interlocked network (MIN) with [an]daisy chain backbone which can efficiently scale up the photoresponsive behavior of mechanical bonds, exhibiting intelligently tunable mechanical properties. In specific, photoresponsive unit of arylazopyrazole (AAP) is embedded onto the axis of each mechanical bond in the [an]daisy chain backbone. Ultraviolet light triggers the trans-to-cis (E/Z) isomerization of the AAP moieties, and when amplified through the [an]daisy chain backbone, it brings about significant changes in the material’s properties. On one hand, the E/Z isomerization significantly shortens the dimension of the [an]daisy chain framework, resulting in a notable increase in the material modulus (from 1.6 to 4.0 MPa). On the other hand, the cis configuration of AAP formed after the isomerization restricts the mobility of the mechanical bonds, resulting in a shorter elongation at break (from 343% to 272%). Our work presents an efficient method for amplifying mechanical bond responsiveness, providing a fresh perspective for the development of intelligent materials.

Mechanically interlocked networks (MINs) built from [2]rotaxane cross-linkers combine high extensibility with enhanced toughness, yet how the interplay between ring mobility and bond scission influences their mechanical responses remains unclear. Here, we employ coarse-grained molecular dynamics simulations to investigate the deformation mechanisms of MINs with varying bond strength, strain rate, and graft density, where a crossover is observed in the deformation mechanism as bond strength increases. Specifically, the weak cross-links lead to scission-dominated deformation with negligible ring sliding, whereas MINs with strong cross-links exhibit profound ring sliding and inhibited bond scission, contributing to the enhanced toughness. Moreover, bond scission and ring sliding exhibit a strain-rate response with the lowest rate favoring scission over sliding, while reducing graft density delays the onset of both processes. These findings provide molecular insights for optimizing MIN mechanics by balancing movable-junction dynamics and cross-link stability.

Studying dynamic chemical behaviors is fundamental to understanding and regulating the dynamic responses and functions of polymer materials. However, real-time, intuitive, and selective visualization of these molecular processes─particularly when multiple dynamic motifs coexist─remains a major challenge. Herein, we introduce surface wrinkles as a visualization platform that directly translates dynamic chemical behaviors in polymers into observable macroscopic morphological changes. Using a dual-cross-linked polymer network (DCN) containing quadruple hydrogen bonds and mechanical bonds as a model system, we fabricate stable wrinkles via modulus mismatch in a bilayer architecture. In situ microscopy reveals that acid-triggered dissociation of quadruple hydrogen bonds causes rapid wrinkle erasure due to network disruption, whereas base-induced rotaxane sliding leads to gradual wrinkle erasure owing to network relaxation, reflecting their distinct dynamic mechanisms and time scales. Rheological analyses on single-cross-linked model networks corroborate these macroscopic observations at the molecular level. Moreover, by programming wrinkle patterns with “write–hide–read” functionality, we achieve macroscopic visualization and differentiation of microscopic dynamic processes. This work establishes surface wrinkling as a powerful and intuitive platform for real-time monitoring of dynamic chemistry and provides valuable insights for designing functional polymer materials with tunable macroscopic properties.

Elastomers with superior mechanical properties are imperative for next generation technologies spanning soft robotics, implantable bioelectronics, and adaptive aerospace systems. However, in conventional chemically crosslinked elastomers, increasing crosslinking density usually enhances modulus while reducing the attainable deformation before fracture, leading to a persistent stiffness–extensibility trade‐off. Here, we report polymer networks incorporating a single type of [2]rotaxane crosslinker that combines hidden length activation and stress redistribution through mechanical bond motion, enabling greater extensibility at comparable stiffness. Increasing the rotaxane crosslinker content raises Young's modulus from 0.08 to 1.83 MPa while decreasing fracture strain from 10.24 to 2.70. The resulting networks exhibit an empirical stiffness–extensibility relationship of , compared with the classical scaling . This relationship corresponds to a smaller proportional loss of extensibility for the same proportional increase in modulus. The fracture energy reaches 5.57 kJ/m ² , compared with 1.01 kJ/m ² for control networks, demonstrating enhanced fracture resistance. Similar stretchability enhancements are observed in networks prepared from other acrylate monomers, supporting the applicability of this design across different acrylate matrices. This work provides a molecular strategy for designing stiff, stretchable, and damage tolerant elastomers.

Elastomers with superior mechanical properties are imperative for next generation technologies spanning soft robotics, implantable bioelectronics, and adaptive aerospace systems. However, in conventional chemically crosslinked elastomers, increasing crosslinking density usually enhances modulus while reducing the attainable deformation before fracture, leading to a persistent stiffness–extensibility trade‐off. Here, we report polymer networks incorporating a single type of [2]rotaxane crosslinker that combines hidden length activation and stress redistribution through mechanical bond motion, enabling greater extensibility at comparable stiffness. Increasing the rotaxane crosslinker content raises Young's modulus from 0.08 to 1.83 MPa while decreasing fracture strain from 10.24 to 2.70. The resulting networks exhibit an empirical stiffness–extensibility relationship of , compared with the classical scaling . This relationship corresponds to a smaller proportional loss of extensibility for the same proportional increase in modulus. The fracture energy reaches 5.57 kJ/m ² , compared with 1.01 kJ/m ² for control networks, demonstrating enhanced fracture resistance. Similar stretchability enhancements are observed in networks prepared from other acrylate monomers, supporting the applicability of this design across different acrylate matrices. This work provides a molecular strategy for designing stiff, stretchable, and damage tolerant elastomers.

Heterodimeric assembly in microtubules (MTs) unifies two functionally complementary tubulin subunits that form similar long-range supramolecular assemblies yet exhibit distinct dynamic behaviors, enabling sophisticated biological functions and providing a powerful paradigm for artificial material design. However, recapitulating such heterodimeric assembly using fully synthetic building blocks remains highly challenging. Here we report a bioinspired heterodimeric A2BB′ assembly approach based on molecular [an]daisy chains ([an]DCs) capable of forming long-range assembled structures, giving rise to a hybrid polymer network (DCHPN) integrating supramolecular and mechanically interlocked [an]DCs. The two structurally similar [an]DC assemblies act as a coupled pair with distinct yet cooperative functions in governing the network dynamics: supramolecular [an]DCs confer dynamic instability analogous to β-tubulin subunits through reversible dissociation, whereas mechanically interlocked [an]DCs function as persistent structural anchors that stabilize the system reminiscent of α-tubulin subunits. Compared with its structurally analogous but purely supramolecular cross-linked control sample, DCHPN exhibits more complex stimuli-responsive behavior, characterized by pronounced dynamic disassembly under external stimuli while retaining polymer-like integrity and enhanced resistance to complete viscous flow upon further activation. This bioinspired strategy offers a prospective pathway for advancing artificial supramolecular assembled materials toward higher-order structural and functional integration.

Propylene carbonate (PC), with a wide liquid‐phase temperature range, represents an ideal electrolyte solvent for lithium‐ion batteries (LIBs) operating under extreme conditions. However, the strong Li ⁺ ‒PC coordination triggers severe solvent co‐intercalation of graphite anodes, leading to irreversible exfoliation and capacity decay. Herein, the mechanically interlocked network (MIN) is proposed to construct the gel polymer electrolyte (GPE) that effectively resolves this long‐standing incompatibility through a dual‐functional molecular design. The crown ether moieties within MIN establish dipole–dipole interactions with PC, disrupting the preferential Li ⁺ ‒PC coordination and thereby suppressing solvent co‐intercalation. The unique topological feature of MINs endows the gel host with high chain mobility, enabling rapid Li ⁺ transport that exceeds conventional GPEs. When integrated into 1 Ah‐level graphite||LiFePO ₄ pouch cells, the MIN‐GPE (MGPE) with PC and LiPF ₆ delivers improved cycling stability over 300 cycles and demonstrates reliable performance across a temperature range from −20°C to 30°C. Furthermore, MGPE exhibits favorable compatibility with high‐voltage LiNi _0.8 Co _0.1 Mn _0.1 O ₂ cathodes. This work highlights the potential of MINs as a versatile framework for GPE design to address PC incompatibility of graphite and sluggish Li ⁺ transport of the polymer host, offering new insights into the development of PC electrolytes for durable LIBs.

Propylene carbonate (PC), with a wide liquid‐phase temperature range, represents an ideal electrolyte solvent for lithium‐ion batteries (LIBs) operating under extreme conditions. However, the strong Li ⁺ ‒PC coordination triggers severe solvent co‐intercalation of graphite anodes, leading to irreversible exfoliation and capacity decay. Herein, the mechanically interlocked network (MIN) is proposed to construct the gel polymer electrolyte (GPE) that effectively resolves this long‐standing incompatibility through a dual‐functional molecular design. The crown ether moieties within MIN establish dipole–dipole interactions with PC, disrupting the preferential Li ⁺ ‒PC coordination and thereby suppressing solvent co‐intercalation. The unique topological feature of MINs endows the gel host with high chain mobility, enabling rapid Li ⁺ transport that exceeds conventional GPEs. When integrated into 1 Ah‐level graphite||LiFePO ₄ pouch cells, the MIN‐GPE (MGPE) with PC and LiPF ₆ delivers improved cycling stability over 300 cycles and demonstrates reliable performance across a temperature range from −20°C to 30°C. Furthermore, MGPE exhibits favorable compatibility with high‐voltage LiNi _0.8 Co _0.1 Mn _0.1 O ₂ cathodes. This work highlights the potential of MINs as a versatile framework for GPE design to address PC incompatibility of graphite and sluggish Li ⁺ transport of the polymer host, offering new insights into the development of PC electrolytes for durable LIBs.

Since the establishment of Carothers’ step-growth gelation theory in 1936, it has been widely accepted that an average functionality greater than two ( f _avg > 2) is a prerequisite for polymer network formation, thereby precluding the direct construction of polymer networks from difunctional monomers. Herein, we introduce the concept of improbable polymer networks (iNETs), whose design is guided by an extended Carothers equation and realized through mechanical bond-mediated step-growth polymerization of difunctional monomers. By employing topological entanglement rather than chemical affinity as the governing design principle, difunctional figure-of-eight rings and linear chains undergo entropy-driven transient threading and are subsequently locked via hydroxy-yne click chemistry, yielding a mechanically interlocked network. The resulting iNET exhibits decent mechanical performance, underpinned by synergistic topological and dynamic mechanisms: sliding of interlocked junctions enables stress redistribution, dissociation of the metal coordination bonds contributes to energy dissipation, and release of latent chain segments affords enhanced extensibility. Meanwhile, mechanically interlocked junctions act as permanent topological anchors, while the entropy-enthalpy co-regulated recovery pathway of the figure-of-eight topology enables rapid and efficient structural restoration after large deformation. This work redefines the conceptual boundaries of gelation theory and establishes a general strategy for constructing polymer networks from difunctional building blocks. It opens new avenues for the rational design of mechanically interlocked materials, in which the classical requirement of f _avg > 2 no longer stands as an insurmountable barrier.

Stereochemistry profoundly affects the physical and mechanical properties of polymers, illustrated by the contrast between elastic natural rubber ( cis -polyisoprene) and the stiffer, less extensible gutta-percha ( trans -isomer). Traditional stereochemistry such as tacticity and cis / trans isomerism primarily governs polymer properties based on fixed structural or conformational factors. Herein, by incorporating the mechanostereochemistry concept into polymers, we demonstrate a stereochemistry paradigm wherein dynamic isomers dictate material properties, thereby defining the unprecedented transient-stereostructure-efficacy mechanism. Specifically, we engineer two mechanically interlocked networks based on [ c 2]daisy chains, where force-triggered intramolecular motion generates mechanostereoisomers with distinct geometric configurations: [ c 2]Daisy chain 1 in MIN- 1 contracts into a fisherman’s knot, whereas [ c 2]daisy chain 2 in MIN- 2 extends into a loop. Due to reduced network elasticity from the loop structure, MIN- 2 exhibits a lower modulus in large-strain shear measurements and less pronounced strain hardening in tensile tests compared to MIN- 1 . Since these mechanostereoisomers are induced by force, material properties show strain-dependent character: both networks perform similarly under small or no strain, but diverge significantly at large strains. Our work expands the conceptual boundaries of polymer stereochemistry and provides insights for designing high-performance materials through stereochemical control.