Haiyan Zheng

Mechanophores provide an in situ and remote tool for quantifying invisible stress in polymers by photonic signals, offering distinct advantages for stress distribution analysis of large-area surfaces and instrument-free stress observation. However, achieving an ideal mechanophore that integrates with sensitive, reversible, and molecular-level stress sensing is attractive yet challenging. Here, we report practical guidance for developing ideal mechanophores that promote the molecular probe’s exciton transition for room-temperature phosphorescence (RTP) under stress, through the “assisted lowest triplet (T1) state” of the adjacent polymer chain. Systematic analyses of numerous organic probes reveal that a small energy gap (ΔEM < 0.4 eV) between the probe’s lowest singlet (S1) and the polymer’s T1 states is an empirical guideline for stress-enhanced RTP. The probe-doped polymer system demonstrates not only a remarkable increase in RTP intensity of over 2000-fold upon 160 MPa but also a low stress threshold of ∼2 MPa, which is robust under 0–10 MPa cyclic pressure loading/unloading over 500 cycles. Such RTP mechanophores enable noninvasive, reversible, and molecular-level stress detection in polymers. Their doped polymers have shown potential applications in various fields for real-time sensing of stress and its uneven distribution through visual afterglow.

Fast and selective lithium ion (Li ⁺ ) transport in polymer electrolytes requires continuous, low‐barrier hopping pathways at room temperature. Here, we construct a multifunctional three‐dimensional polymer network in which solid succinonitrile (SN) dynamically couples adjacent ether and ester coordination sites, creating a bridge‐mediated, nanoscopically continuous Li ⁺ pathway. High‐field (up to 18.8 T) multinuclear multidimensional solid‐state nuclear magnetic resonance directly reveals that SN cooperates with polymer chains to form an interconnected coordination network. Acting as a dynamic molecular bridge, this network shortens Li─O transport distances to below 7 Å and accelerates Li ⁺ hopping. Meanwhile, boron‐containing moieties associate with bis(fluorosulfonyl)imide anions (FSI) and restrict their local mobility, enhancing Li ⁺ selectivity. Variable‐temperature measurements confirm accelerated local Li ⁺ dynamics with a correlation activation energy of 0.07 eV and suppressed anion motion. Consequently, the electrolyte delivers an ionic conductivity of 1.31 mS cm ⁻¹ and a Li ⁺ transference number of 0.61 at 30°C. It also enables stable cycling with high‐loading cathodes, retaining 89.8% capacity after 200 cycles with LiFePO ₄ (12.9 mg cm ⁻² ) and robustly operating with LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (10.0 mg cm ⁻² ). This work establishes a molecular structure‐dynamics framework for regulating Li ⁺ hopping and provides a practical strategy for advanced polymer electrolytes through rational engineering of dynamic local coordination environments.

Single-metal-atom chains (SMACs) represent the ultimate limit of one-dimensional nanostructures. They serve as archetypal model systems for condensed matter physics and constitute fundamental building blocks for next-generation nanoelectronics. However, synthesis of SMACs suitable for practical applications remains challenging. In this work, we create micrometer-long, carbon-sheathed copper SMACs at milligram scale by compressing β-copper phthalocyanine to above 21 gigapascals. The SMACs are in atom-scale ordering, are isolable through acid-assisted exfoliation, and exhibit exceptional stability, with Cu-Cu distance confined at 2.57 angstroms. Anisotropic conductance and antiferromagnetic interactions are suggested by experimental and computational results. This work establishes a universal synthetic strategy for sheathed SMACs, positioning them as a compelling platform for prospective electronic and spintronic applications.

Pressure is a powerful tool to modulate hybrid metal halides (HMHs), but its effects are often reversed upon decompression. Here, using the unsaturated m-aminophenylacetylene (m-APA) cation, we report pressure-induced polymerization (PIP) as a strategy for irreversible band-structure engineering in three heterostructures as HMH crystals: (m-APA)₂Pb₃I₈, (m-APA)₂PbBr₄, and (m-APA)PbCl₃. Distinct polymerization pathways yield novel ambient-stable phases with narrowed band gaps and reconfigured band alignments. The resulting polymeric cations exhibit varied sp²/sp³-C ratios, which significantly tune the electronic coupling across organic-inorganic interfaces. Specifically, P-(m-APA)₂Pb₃I₈ retains type I alignment with gap narrowing driven by chemical pressure on the inorganic sublattice, while P-(m-APA)₂PbBr₄ undergoes a type I to type II transition, and P-(m-APA)PbCl₃ transforms from type II to reversed-type I via organic band-edge reconstruction. This work demonstrates PIP as a novel and general approach to permanently tailor the electronic structures of HMHs, enabling functional design through the controlled covalent transformation of organic cations under high pressure.

Mechanochemical radical polymerization has unique advantages in the synthesis of polymers due to its reduced solvent consumption and adaptability of insoluble monomers. However, it suffers from the uncontrollable degradation of the formed polymers during reaction, and a new synthetic strategy with precise controllability needs to be developed. Here, by employing high static pressure up to 30 GPa, we found 1,3,5-trifluorobenzene undergoes radical polymerization by breaking the conjugated π-bonds and forms a carbon nanothread with high selectivity (Polymer-I polymorph). Based on the crystal structure at the threshold pressure and the calculated energy barriers for the bonding pathway, we concluded that the benzene rings react via a radical 1,2-addition pathway. Our work highlights that high pressure is a robust method to initiate solid-state radical polymerization, even for very stable aromatics, and offers fresh insights for the synthesis of polymeric carbon-based materials with high selectivity.

Graphane shares the same two-dimensional honeycomb structure of graphene, but its saturated carbon skeleton gives rise to a bandgap and therefore provides more possibilities for the development of novel carbon-based semiconductors. However, the hydrogenation of graphene usually leads to disordered and incompletely hydrogenated graphane, and the precise synthesis of graphane with a specific configuration is still very challenging. Here, we synthesized a crystalline graphane nanoribbon (GANR) via pressure-induced polymerization of 2,2'-bipyrazine (BPZ). By performing Rietveld refinement of in situ neutron diffraction data, nuclear magnetic resonance spectroscopy, infrared spectra, and theoretical calculation, we found that BPZ experienced Diels-Alder polymerization between the π···π stacked aromatic rings and formed extended boat-GANR structures with exceptional long-range order. The unreacted -C═N- groups bridge the two ends of the boat and are ready for further functionalization. The GANR has a bandgap of 2.25 eV, with booming photoelectric response (I_ON/I_OFF = 18.8). Our work highlights that high-pressure topochemical polymerization is a promising method for the precise synthesis of graphane with specific structure and desired properties.

Polymer electrolytes (PEs) show great promise in next-generation solid-state batteries. The interactions between functional monomers and lithium salts in PEs remain ambiguous, constraining the material design strategy aimed at optimizing the electrochemical performance. Here, we report on the local spatial interactions among the components in polycarbonate-based electrolytes, as determined through nuclear magnetic resonance (NMR) techniques. We used molecular dynamics simulations to rationalize the spatial distribution of ions and its effect on the coordination of anions and cations. The local dynamics of the anions and cations were further revealed from an ion dynamics perspective using variable temperature NMR techniques, shedding light on how ion mobility is affected by different spatial interactions. Finally, we clearly delineate how battery performances are affected by local spatial interactions. Our findings provide direct experimental evidence, revealing how spatial interactions affect ion diffusion dynamics at the molecular level. Overall, this work provides valuable guidance for the design and mechanistic understanding of PEs.

The Alder-ene reaction is a chemical reaction between an alkene with an allylic hydrogen, and it provides an efficient method to construct the C-C bond. Traditionally, this reaction requires catalysts, high temperatures, or photocatalysis. In this study, we reported a high-pressure-induced solid-state Alder-ene reaction of 1-hexene at room temperature without a catalyst. 1-Hexene crystallizes at 4.3 GPa and polymerizes at 18 GPa, forming olefins. By exploring gas chromatography-mass spectrometry, we discovered that 1-hexene generates dimeric products through the Alder-ene reaction under high pressures. The in situ neutron diffraction shows that the reaction process did not obey the topochemical rule. A six-membered ring transition state including one C-H σ bond and two alkene π bonds was evidenced by the theoretical calculation, whose energy obviously decreased when compressed to 20 GPa. Our work offers a novel and promising method to realize the Alder-ene reaction at room temperature without a catalyst, expanding the application of this important reaction.

Nonbenzenoid graphene nanoribbons such as biphenylene networks have gained increasing attention owing to their promising electronic and transport properties, but their scalable synthesis is still a huge challenge. Pressure-induced topochemical polymerization is an effective method to assemble molecular units into extended carbon materials, and the structure and properties of the carbon material can be tuned by modifying its molecular precursors. Herein, by directly compressing biphenylene at room temperature, we successfully synthesized crystalline biphenylene nanoribbons in milligram scale. By combining the spectroscopy and single crystal X-ray diffraction methods as well as theoretical calculation, we found that biphenylene experiences a minor phase transition above 3 GPa, and two phenyls in biphenylene undergo sequential para-polymerization along the a-axis to form a ribbon structure at 14 GPa. Our work provides an important reference for the high-pressure reaction of aromatics and the synthesis of complex nanoribbons.

Tungsten bronze oxides have emerged as attractive materials for energy storage owing to their fast charge-discharge property. However, the internal weakness of low capacity and short cycling performance impedes their development in wide application. In this work, the tungsten bronze W₃Nb₂O₁₄ nanorods with preferred orientation (001) were prepared by hydrothermal method for the first time. It not only displays high-rate performance but also exhibits high capacity (201 mA h g^-1 at 0.2 C) and long cycling property (80% capacity retention at 50 C after 3000 cycles). Notably, in situ XRD revealed the c evolution frustrates the V increase, and the maximum unit-cell volume expansion is only 2.9% during lithiation/delithiation, reflecting the long cycle performance is benefit from the low strain and preferred orientation. The ex-situ ⁶Li NMR spectra revealed that the lithiation and delithiation present preference based on the size of tunnels in the crystal framework.