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题名

Direct Observation of Biaxial Nematic Order in Auxetic Liquid Crystal Elastomers

作者
通讯作者Raistrick, Thomas
发表日期
2023-01
DOI
发表期刊
EISSN
1996-1944
卷号16期号:1
摘要
Auxetic materials exhibit a negative Poisson’s ratio, i.e., they become thicker rather than thinner in at least one dimension when strained. Recently, a nematic liquid crystal elastomer (LCE) was shown to be the first synthetic auxetic material at a molecular level. Understanding the mechanism of the auxetic response in LCEs is clearly important, and it has been suggested through detailed Raman scattering studies that it is related to the reduction of uniaxial order and emergence of biaxial order on strain. In this paper, we demonstrate direct observation of the biaxial order in an auxetic LCE under strain. We fabricated ~100 μm thick LCE strips with complementary geometries, exhibiting either planar or homeotropic alignment, in which the auxetic response is seen in the thickness or width of the sample, respectively. Polarized Raman scattering measurements on the planar sample show directly the reduction in the uniaxial order parameters on strain and suggest the emergence of biaxial order to mediate the auxetic response in the sample thickness. The homeotropic sample is studied via conoscopy, allowing direct observation of both the auxetic response in the width of the sample and increasing biaxiality in the LCE as it is strained. We verified that the mechanism of the auxetic response in auxetic LCEs is due to the emergence of the biaxial order and conclude such materials can be added to the small number of biaxial nematic systems that have been observed. Importantly, we also show that the mechanical Frèedericksz transition seen in some LCEs is consistent with a strain-induced transition from an optically positive to an optically negative biaxial system under strain, rather than a director rotation in a uniaxial system.
© 2022 by the authors.
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收录类别
EI ; SCI
语种
英语
学校署名
其他
资助项目
This research was funded by the Engineering and Physical Sciences Research Council (EPSRC EP/V054724/1).
WOS研究方向
Chemistry ; Materials Science ; Metallurgy & Metallurgical Engineering ; Physics
WOS类目
Chemistry, Physical ; Materials Science, Multidisciplinary ; Metallurgy & Metallurgical Engineering ; Physics, Applied ; Physics, Condensed Matter
WOS记录号
WOS:000908975500001
出版者
EI入藏号
20230213360275
EI主题词
Elastomers ; Nematic liquid crystals ; Plastics
EI分类号
Light/Optics:741.1 ; Polymer Products:817.1 ; Elastomers:818.2
来源库
EV Compendex
引用统计
被引频次[WOS]:7
成果类型期刊论文
条目标识符http://sustech.caswiz.com/handle/2SGJ60CL/519746
专题工学院_电子与电气工程系
作者单位
1.School of Physics and Astronomy, University of Leeds, Leeds; LS2 9JT, United Kingdom
2.Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen; 518055, China
第一作者单位电子与电气工程系
推荐引用方式
GB/T 7714
Wang, Zhenming,Raistrick, Thomas,Street, Aidan,et al. Direct Observation of Biaxial Nematic Order in Auxetic Liquid Crystal Elastomers[J]. Materials,2023,16(1).
APA
Wang, Zhenming,Raistrick, Thomas,Street, Aidan,Reynolds, Matthew,Liu, Yanjun,&Gleeson, Helen F..(2023).Direct Observation of Biaxial Nematic Order in Auxetic Liquid Crystal Elastomers.Materials,16(1).
MLA
Wang, Zhenming,et al."Direct Observation of Biaxial Nematic Order in Auxetic Liquid Crystal Elastomers".Materials 16.1(2023).
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