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Mechanically interlocked monolayer and bilayer two-dimensional polymers with high elastic modulus
Original press release from Max Planck Institute of Microstructure Physics, Halle/Saale, Germany; 13 Nov 2025
Published on in NEWS
b) TEM images of MI-M2DP and MI-B2DP.
c) Mechanical properties of MI-M2DP, 2×MI-M2DP and MI-B2DP measured by AFM nanoindentation.
© Springer-Nature
In a recent article published in Nature Synthesis, researchers from the Max Planck Institute of Microstructure Physics and TU Dresden reported an on-water surface synthesis strategy for the construction of mechanically interlocked monolayer and bilayer 2D polymers. This study sheds light on the controlled synthesis of crystalline 2D polymer at the monolayer or bilayer level and provides potential avenues to address the challenges of exploring the interlayer structure-property relationships.
Two-dimensional polymers (2DPs) and their layer-stacked covalent organic frameworks (2D COFs), are a class of crystalline materials exhibiting periodic order in two orthogonal directions. In these organic 2D crystals, adjacent layers are typically stacked by weak van der Waals forces, π–π interactions, or hydrogen bonding. While extensive research has elucidated their in-plane structures and properties, interlayer interactions across the third dimension present an additional, yet less explored, avenue for structural and functional tunability. Controlled stacking into bilayers gives rise to emergent physical and chemical phenomena absent in the monolayer limit, driven by proximity effects such as interlayer electronic coupling and interfacial symmetry breaking. For example, slight rotational misalignment between layers produces moiré superlattices with spatially modulated electronic or excitonic features, while stacking alters the band gap or introduces new states near the Fermi level. Likewise, weak interlayer interactions enable sliding or decoupling between layers, reducing overall mechanical strength. These observations underscore the importance of constructing both monolayer and bilayer 2DPs to probe interlayer structure–property relationships. Top-down approaches, including physical and chemical exfoliation, can yield ultrathin layers, but often suffer from poor structural integrity and non-uniform thickness. In contrast, bottom-up strategies, such as on-surface synthesis and Langmuir-Blodgett techniques, have demonstrated success in producing monolayer 2DPs. However, extending these strategies to bilayer, whether via direct synthesis or layer-by-layer transfer, invariably disrupts structural uniformity, as interlayer interactions and offsets introduce disorder. Therefore, precise control over 2DP thickness from monolayer to bilayer—while preserving well-defined in-plane structures—remains a synthetic challenge.
A recent article by researchers from the Max Planck Institute of Microstructure Physics and TU Dresden, published in Nature Synthesis, report the on-water surface synthesis of crystalline mechanically interlocked monolayer and bilayer 2DP (MI-M2DP and MI-B2DP) films by embedding macrocyclic molecules (MCMs) with one and two cavities into 2DP backbones. The incorporation of bulky MCMs introduces periodic mechanical bonds that precisely control interlayer interlocking, enabling selective monolayer or bilayer 2DP formation. Both MI-M2DP and MI-B2DP exhibit homogenous, large-area films with ordered hexagonal pores and high modulus. MI-B2DP demonstrates an exceptionally high effective Young's modulus of 151±16 GPa (indentation method), surpassing MI-M2DP (90±14 GPa), vdW-stacked MI-M2DPs (46±11 GPa), and other reported multilayer 2DPs (< 50 GPa). Modeling confirms that the mechanical interlocking minimizes interlayer sliding and reinforces the structure. This study advances the controlled synthesis of crystalline two-dimensional polymers at the monolayer and bilayer levels, offering new insights and strategies to overcome existing challenges in probing interlayer structure–property relationships.
The paper entitled "Mechanically interlocked monolayer and bilayer two-dimensional polymers with high elastic modulus” by Ye Yang, André Knapp, David Bodesheim, Alexander Croy, Mike Hambsch, Ilka Hermes, Chandrasekhar Naisa, Darius Pohl, Bernd Rellinghaus, Changsheng Zhao, Stefan C. B. Mannsfeld, Gianaurelio Cuniberti, Zhiyong Wang, Renhao Dong, Andreas Fery, and Xinliang Feng can be found at: https://www.nature.com/articles/s44160-025-00930-4.
Contact:
Ye Yang
E-mail: ye.yang@mpi-halle.mpg.de
Original Publication:
Ye Yang, André Knapp, David Bodesheim, Alexander Croy, Mike Hambsch, Ilka Hermes, Chandrasekhar Naisa, Darius Pohl, Bernd Rellinghaus, Changsheng Zhao, Stefan C. B. Mannsfeld, Gianaurelio Cuniberti, Zhiyong Wang, Renhao Dong, Andreas Fery, and Xinliang Fen
Mechanically interlocked monolayer and bilayer two-dimensional polymers with high elastic modulus
DOI: 10.1038/s44160-025-00930-4
Nature Synthesis 2025