Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Single crystals of mechanically entwined helical covalent polymers


Double helical conformation of polymer chains is widely observed in biomacromolecules and plays an essential role in exerting their biological functions, such as molecular recognition and information storage. It has remained challenging, however, to prepare synthetic helical polymers, and those that exist have mainly been limited to single-stranded polymers or short oligomeric double helices. Here, we report the synthesis of covalent helical polymers, with a high molecular weight, from the achiral monomer hexahydroxytriphenylene through to spiroborate formation. Polymerization and crystallization occurred simultaneously under solvothermal conditions to form single crystals of the resulting helical covalent polymers. Characterization by single-crystal X-ray diffraction showed that each crystal consisted of pairs of mechanically entwined polymers. No strong non-covalent interactions were observed between the two helical polymers that formed a pair; instead, each strand interacted with neighbouring pairs through hydrogen bonding. Each individual crystal was made up of helical polymers of the same handedness, but the crystallization process produced a racemic conglomerate, with equal amounts of right-handed and left-handed crystals.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Fig. 1: The helical covalent polymer.
Fig. 2: Single-crystal structures of 1 showing a double helical conformation.
Fig. 3: The HCP helical chirality and PXRD patterns.
Fig. 4: The HCP morphology and mechanical properties.

Data availability

Experimental data and characterization data are provided in the Supplementary Information. Crystallographic data for the two crystals of 1 (tentatively assigned to right-handed) reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2017159 (HCP crystal 1) and 2034057 (HCP crystal 2). Copies of the data can be obtained free of charge via


  1. Watson, J. D. & Crick, F. H. C. Molecular structure of nucleic acids: a structure for deoxyribose nucleic acid. Nature 171, 737–738 (1953).

    Article  CAS  Google Scholar 

  2. Yashima, E. et al. Supramolecular helical systems: helical assemblies of small molecules, foldamers, and polymers with chiral amplification and their functions. Chem. Rev. 116, 13752–13990 (2016).

    Article  CAS  Google Scholar 

  3. Hill, D. J., Mio, M. J., Prince, R. B., Hughes, T. S. & Moore, J. S. A field guide to foldamers. Chem. Rev. 101, 3893–4012 (2001).

    Article  CAS  Google Scholar 

  4. Zhang, D.-W., Zhao, X., Hou, J.-L. & Li, Z.-T. Aromatic amide foldamers: structures, properties, and functions. Chem. Rev. 112, 5271–5316 (2012).

    Article  CAS  Google Scholar 

  5. Nakano, T. & Okamoto, Y. Synthetic helical polymers: conformation and function. Chem. Rev. 101, 4013–4038 (2001).

    Article  CAS  Google Scholar 

  6. Yashima, E., Maeda, K., Iida, H., Furusho, Y. & Nagai, K. Helical polymers: synthesis, structures, and functions. Chem. Rev. 109, 6102–6211 (2009).

    Article  CAS  Google Scholar 

  7. Percec, V. et al. Steric communication of chiral information observed in dendronized polyacetylenes. J. Am. Chem. Soc. 128, 16365–16372 (2006).

    Article  CAS  Google Scholar 

  8. Percec, V. et al. Self‐assembling phenylpropyl ether dendronized helical polyphenylacetylenes. Chem. Eur. J. 13, 9572–9581 (2007).

    Article  Google Scholar 

  9. Percec, V. et al. Synthesis, structural, and retrostructural analysis of helical dendronized poly(1‐naphthylacetylene)s. J. Polym. Sci. A 45, 4974–4987 (2007).

    Article  CAS  Google Scholar 

  10. Rudick, J. G. & Percec, V. Nanomechanical function made possible by suppressing structural transformations of polyarylacetylenes. Macromol. Chem. Phys. 209, 1759–1768 (2008).

    Article  CAS  Google Scholar 

  11. Motoshige, A., Mawatari, Y., Motoshige, R., Yoshida, Y. & Tabata, M. Contracted helix to stretched helix rearrangement of an aromatic polyacetylene prepared in n‐hexane with [Rh(norbornadiene)Cl]2‐triethylamine catalyst. J. Polym. Sci. A 51, 5177–5183 (2013).

    Article  CAS  Google Scholar 

  12. Liu, X.-Q., Wang, J., Yang, S. & Chen, E.-Q. Self-organized columnar phase of side-chain liquid crystalline polymers: to precisely control the number of chains bundled in a supramolecular column. ACS Macro Lett. 3, 834–838 (2014).

    Article  CAS  Google Scholar 

  13. Lehn, J.-M. et al. Spontaneous assembly of double-stranded helicates from oligobipyridine ligands and copper (i) cations: structure of an inorganic double helix. Proc. Natl Acad. Sci. USA 84, 2565–2569 (1987).

    Article  CAS  Google Scholar 

  14. Berl, V., Huc, I., Khoury, R. G., Krische, M. J. & Lehn, J.-M. Interconversion of single and double helices formed from synthetic molecular strands. Nature 407, 720–723 (2000).

    Article  CAS  Google Scholar 

  15. Miwa, K., Furusho, Y. & Yashima, E. Ion-triggered spring-like motion of a double helicate accompanied by anisotropic twisting. Nat. Chem. 2, 444–449 (2010).

    Article  CAS  Google Scholar 

  16. Ousaka, N. et al. Spiroborate-based double-stranded helicates: meso-to-racemo isomerization and ion-triggered springlike motion of the racemo-helicate. J. Am. Chem. Soc. 140, 17027–17039 (2018).

    Article  CAS  Google Scholar 

  17. Wang, Y. et al. Double helical conformation and extreme rigidity in a rodlike polyelectrolyte. Nat. Commun. 10, 801 (2019).

    Article  Google Scholar 

  18. Kusanagi, H., Chatani, Y. & Tadokoro, H. The crystal structure of isotactic poly(methyl methacrylate): packing-mode of double stranded helices. Polymer 35, 2028–2039 (1994).

    Article  CAS  Google Scholar 

  19. Liu, Y. et al. Weaving of organic threads into a crystalline covalent organic framework. Science 351, 365–369 (2016).

    Article  CAS  Google Scholar 

  20. Leiras, S., Freire, F., Quiñoá, E. & Riguera, R. Reversible assembly of enantiomeric helical polymers: from fibers to gels. Chem. Sci. 6, 246–253 (2015).

    Article  CAS  Google Scholar 

  21. Beaudoin, D., Maris, T. & Wuest, J. D. Constructing monocrystalline covalent organic networks by polymerization. Nat. Chem. 5, 830–834 (2013).

    Article  CAS  Google Scholar 

  22. Evans, A. M. et al. Seeded growth of single-crystal two-dimensional covalent organic frameworks. Science 361, 52–57 (2018).

    Article  CAS  Google Scholar 

  23. Ma, T. et al. Single-crystal X-ray diffraction structures of covalent organic frameworks. Science 361, 48–52 (2018).

    Article  CAS  Google Scholar 

Download references


We thank V. Ferguson and A. Tomaschke for the nano-indentation tests, D. Gin for the assistance with the PXRD facility, B. Lama for the solid-state NMR measurements and X. Tang for circular dichroism measurements. We thank the University of Colorado Boulder for funding support. Y.C. acknowledges support from the National Science Foundation of China (91856204) and Key Project of Basic Research of Shanghai (18JC1413200). W.G. is supported by the China Postdoctoral Science Foundation (2019M661482). Z.Z. and T.J. are sponsored by the Shanghai Pujiang Talent Plan (no. 20PJ1414100) and the National Natural Science Foundation of China (62005198). X.C. is supported by the National Natural Science Foundation of China (no. 61925504). This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility, under contract no. DE-AC02-05CH11231.

Author information

Authors and Affiliations



Y.H., Y.J. and W.Z. conceived the idea and led the project. Y.H., H.C. and J.W. conducted the synthesis and crystal growth. W.G., Y.C. and S.J.T. carried out single-crystal study and structure refinement. Z.Z., T.J. and X.C. performed the AFM test and infrared scattering scanning nearfield optical microscopy measurements. Y.J. and W.Z. wrote the manuscript with help from Y.H. and Y.C. All authors discussed and revised the manuscript.

Corresponding author

Correspondence to Wei Zhang.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Chemistry thanks the anonymous reviewers for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–13, Discussion and Tables 1–5.

Supplementary Data 1

Crystallographic data of the helical covalent polymer, crystal 1; CCDC 2017159.

Supplementary Data 2

Crystallographic data of the helical covalent polymer, crystal 2; CCDC 2034057.

Supplementary Data 3

Source data for Supplementary Fig. 7.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hu, Y., Teat, S.J., Gong, W. et al. Single crystals of mechanically entwined helical covalent polymers. Nat. Chem. 13, 660–665 (2021).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing