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Mouldable liquid-crystalline elastomer actuators with exchangeable covalent bonds

Nature Materials volume 13, pages 36–41 (2014)Cite this article

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Abstract

Liquid-crystal elastomers (LCEs) are a class of actively moving polymers with remarkable practical potential for converting external stimuli into mechanical actuation1. However, real-world applications of LCEs are lacking because macroscopic orientation of liquid-crystal order, which is required for reversible actuations2,3, is hard to achieve in practice. Here we show that the processing bottleneck of LCEs can be overcome by introducing exchangeable links in place of permanent network crosslinks, a concept previously demonstrated for vitrimers4,5. Liquid-crystal elastomers with exchangeable links (xLCEs) are mouldable, allow for easy processing and alignment, and can be subsequently altered through remoulding with different stress patterns, thus opening the way to practical xLCE actuators and artificial muscles. Surprisingly, instead of external-stress relaxation through the creep of non-liquid-crystal transient networks with exchangeable links6,7, xLCEs develop strong liquid-crystal alignment as an alternative mechanism of mechanical relaxation.

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Figure 1: Structure and processing of an epoxy network capable of transesterification.
Figure 2: Shape-memory effects in a non-aligned polydomain xLCE.
Figure 3: Thermo-mechanical effects in a non-aligned polydomain xLCE.
Figure 4: The scheme of xLCE processing leading to an equilibrium monodomain alignment, and its reversal.
Figure 5: Equilibrium thermal actuation of a monodomain xLCE, in different sample configurations.

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Acknowledgements

This research was supported by the National Science Foundation of China (nos 21274075 and 51203086) and the National 973 Project (no. 2011CB935700).

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  1. Zhiqiang Pei and Yang Yang: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Chemistry, The Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology, Tsinghua University, Beijing 100084, China

    Zhiqiang Pei, Yang Yang, Qiaomei Chen, Yen Wei & Yan Ji

  2. Cavendish Laboratory, University of Cambridge, Cambridge CB3 OHE, UK

    Eugene M. Terentjev

Authors
  1. Zhiqiang Pei
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  2. Yang Yang
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  4. Eugene M. Terentjev
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Contributions

Y.J. and E.M.T. developed the concept, Y.J. and Y.W. arranged the funding and infrastructure for the project, Z.P., Y.Y. and Y.J. performed the experiments, Q.C. participated in the synthesis of xLCEs, and Y.J., E.M.T. and Y.W. contributed to writing the paper.

Corresponding authors

Correspondence to Eugene M. Terentjev or Yan Ji.

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The authors declare no competing financial interests.

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Pei, Z., Yang, Y., Chen, Q. et al. Mouldable liquid-crystalline elastomer actuators with exchangeable covalent bonds. Nature Mater 13, 36–41 (2014). https://doi.org/10.1038/nmat3812

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