Article (Scientific journals)
Sub-second dynamic phototuning of alignment in azodendrimer-doped nematic liquid crystal shells
Noh, Junghyun; Jampani, Venkata; Haba, Osamu et al.
2018In Journal of Molecular Liquids, 267, p. 197-204
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Keywords :
Nematic liquid crystal; Azodye dendrimer; Photoswitching of alignment; Phase separation
Abstract :
[en] The alignment of nematic liquid crystal 5CB in micron-thick shells, suspended in and containing aqueous liquid phases, can be rapidly switched between radial (homeotropic) and tangential (planar) director field by doping them with a photoresponsive dendrimer with multiple azobenzene moieties in the branches. The dendrimer spontaneously segregates to the inner as well as outer shell interfaces, folding into an amphiphilic conformation irrespective of the sign of interface curvature. The branches are directed into the liquid crystal, inducing a homeotropic ground state. Upon UV irradiation, the trans-cis isomerization of azobenzene triggers immediate switching to planar alignment. The very fast realignment and the simultaneous response throughout the shell leads to an initially random planar director field, with many topological defects of both positive and negative signs becoming visible within a second of irradiation. All but two +1 defects quickly annihilate, and the remaining defect pair moves up towards the thinnest part of the shell to form the planar steady state. By illuminating with visible light the homeotropic alignment is quickly recovered. By exchanging the solvent used for assisting the dendrimer dissolution, also dynamic phase separation phenomena can be studied in the shells, revealing that the dendrimer solubility in 5CB is greater in the UV-induced cis state than in the trans ground state.
Disciplines :
Physics
Author, co-author :
Noh, Junghyun ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Jampani, Venkata ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Haba, Osamu;  Yamagata University
Yonetake, Koichiro;  Yamagata University
Takezoe, Hideo;  Toyota Physical and Chemical Research Institute
Lagerwall, Jan  ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
External co-authors :
yes
Language :
English
Title :
Sub-second dynamic phototuning of alignment in azodendrimer-doped nematic liquid crystal shells
Publication date :
01 October 2018
Journal title :
Journal of Molecular Liquids
ISSN :
0167-7322
Publisher :
Elsevier, Netherlands
Special issue title :
Special Issue Dedicated to the Memory of Professor Y. Reznikov
Volume :
267
Pages :
197-204
Peer reviewed :
Peer Reviewed verified by ORBi
Focus Area :
Physics and Materials Science
European Projects :
H2020 - 648763 - INTERACT - Intelligent Non-woven Textiles and Elastomeric Responsive materials by Advancing liquid Crystal Technology
FnR Project :
FNR6992111 - Ultrathin Liquid-crystal Shells For Smart Colloids, 2013 (15/04/2014-14/04/2018) - Junghyun Noh
Funders :
CE - Commission Européenne [BE]
Available on ORBilu :
since 13 December 2018

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