Berrow, S.R. orcid.org/0000-0003-3764-1613, Raistrick, T. orcid.org/0000-0002-6227-6550, Mandle, R.J. orcid.org/0000-0001-9816-9661 et al. (1 more author) (2024) Structure–Property Relationships in Auxetic Liquid Crystal Elastomers—The Effect of Spacer Length. Polymers, 16 (14). 1957. ISSN 2073-4360
Abstract
Auxetics are materials displaying a negative Poisson’s ratio, i.e., getting thicker in one or both transverse axes when subject to strain. In 2018, liquid crystal elastomers (LCEs) displaying auxetic behaviour, achieved via a biaxial reorientation, were first reported. Studies have since focused on determining the physics underpinning the auxetic response, with investigations into structure–property relationships within these systems so far overlooked. Herein, we report the first structure–property relationships in auxetic LCEs, examining the effect of changes to the length of the spacer chain. We demonstrate that for LCEs with between six and four carbons in the spacer, an auxetic response is observed, with the threshold strain required to achieve this response varying from 56% (six carbon spacers) to 81% (four carbon spacers). We also demonstrate that Poisson’s ratios as low as −1.3 can be achieved. Further, we report that the LCEs display smectic phases with spacers of seven or more carbons; the resulting internal constraints cause low strains at failure, preventing an auxetic response. We also investigate the dependence of the auxetic threshold on the dynamics of the samples, finding that when accounting for the glass transition temperature of the LCEs, the auxetic thresholds converge around 56%, regardless of spacer length.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2024 by the authors. This is an open access article under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. |
Keywords: | liquid crystal elastomer; auxetic; spacer; structure-property relationships; mechanical metamaterials |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Soft Matter Physics (Leeds) |
Funding Information: | Funder Grant number EPSRC (Engineering and Physical Sciences Research Council) EP/V054724/1 MRC (Medical Research Council) MR/W006391/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Jul 2024 12:37 |
Last Modified: | 24 Jan 2025 11:09 |
Status: | Published |
Publisher: | MDPI |
Identification Number: | 10.3390/polym16141957 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:214595 |