Article (Scientific journals)
Isotropic–isotropic phase separation and spinodal decomposition in liquid crystal–solvent mixtures
Reyes, Catherine; Baller, Jörg; Araki, Takeaki et al.
2019In Soft Matter, 15, p. 6044-6054
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Keywords :
liquid crystal; 5CB; phase separation; ethanol; binary mixtures; water; phase diagram; free energy; concentration gradient; polarized optical microscopy; DSC; numerical simulation
Abstract :
[en] Phase separation in mixtures forming liquid crystal (LC) phases is an important yet under- appreciated phenomenon that can drastically influence the behaviour of a multi-component LC. Here we demonstrate, using polarising microscopy with active cooling as well as differential scanning calorimetry, that the phase diagram for mixtures of the LC-forming compound 4’-n- pentylbiphenyl-4-carbonitrile (5CB) with ethanol is surprisingly complex. Binary mixtures reveal a broad miscibility gap that leads to phase separation between two distinct isotropic phases via spinodal decomposition or nucleation and growth. On further cooling the nematic phase enters on the 5CB-rich side, adding to the complexity. Significantly, water contamination dramatically raises the temperature range of the miscibility gap, bringing up the critical temperature for spinodal de- composition from ∼ 2◦C for the anhydrous case to > 50◦C if just 3 vol.% water is added to the ethanol. We support the experiments with a theoretical treatment that qualitatively reproduces the phase diagrams as well as the transition dynamics, with and without water. Our study highlights the impact of phase separation in LC-forming mixtures, spanning from equilibrium coexistence of multiple liquid phases to non-equilibrium effects due to persistent spatial concentration gradients.
Disciplines :
Physics
Engineering, computing & technology: Multidisciplinary, general & others
Materials science & engineering
Chemical engineering
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Chemistry
Author, co-author :
Reyes, Catherine ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Baller, Jörg ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Araki, Takeaki;  Kyoto University > Department of Physics
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 :
Isotropic–isotropic phase separation and spinodal decomposition in liquid crystal–solvent mixtures
Publication date :
14 June 2019
Journal title :
Soft Matter
ISSN :
1744-6848
Publisher :
Royal Society of Chemistry, Cambridge, United Kingdom
Volume :
15
Pages :
6044-6054
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
Funders :
CE - Commission Européenne [BE]
Available on ORBilu :
since 28 August 2019

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