Probing the in-plane liquid-like behavior of liquid crystal elastomers

Haruki Tokumoto; Hao Zhou; Asaka Takebe; Kazutaka Kamitani; Ken Kojio; Atsushi Takahara; Kaushik Bhattacharya; Kenji Urayama

doi:10.1126/sciadv.abe9495

Probing the in-plane liquid-like behavior of liquid crystal elastomers

Sci Adv. 2021 Jun 18;7(25):eabe9495. doi: 10.1126/sciadv.abe9495. Print 2021 Jun.

Authors

Haruki Tokumoto¹, Hao Zhou², Asaka Takebe¹, Kazutaka Kamitani³, Ken Kojio³, Atsushi Takahara³, Kaushik Bhattacharya⁴, Kenji Urayama⁵

Affiliations

¹ Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan.
² Department of Mechanical and Civil Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
³ Institute for Materials Chemistry and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan.
⁴ Department of Mechanical and Civil Engineering, California Institute of Technology, Pasadena, CA 91125, USA. bhatta@caltech.edu urayama@kit.ac.jp.
⁵ Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan. bhatta@caltech.edu urayama@kit.ac.jp.

Abstract

When isotropic solids are unequally stretched in two orthogonal directions, the true stress (force per actual cross-sectional area) in the larger strain direction is typically higher than that in the smaller one. We show that thiol-acrylate liquid crystal elastomers with polydomain texture exhibit an unusual tendency: The true stresses in the two directions are always identical and governed only by the area change in the loading plane, independently of the combination of imposed strains in the two directions. This feature proves a previously unidentified state of matter that can vary its shape freely with no extra mechanical energy like liquids when deformed in the plane. The theory and simulation that explain the unique behavior are also provided. The in-plane liquid-like behavior opens doors for manifold applications, including wrinkle-free membranes and adaptable materials.

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