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Isotropic-isotropic phase separation and spinodal decomposition in liquid crystal-solvent mixtures
Catherine G Reyes1, Jörg Baller1, Takeaki Araki2
1Physics and Materials Science Research Unit, University of Luxembourg, 162a, Avenue de la Faencerie, L-1511, Luxembourg. jan.lagerwall@lcsoftmatter.com.
Soft Matter
|June 22, 2019
Summary
Phase separation in liquid crystal (LC) mixtures is complex. Water contamination significantly widens the miscibility gap, impacting phase behavior and critical temperatures in 5CB-ethanol systems.
Area of Science:
- Materials Science
- Physical Chemistry
- Liquid Crystals
Background:
- Phase separation in multi-component liquid crystal (LC) systems is crucial for material behavior.
- Understanding miscibility gaps and phase diagrams is key to controlling LC properties.
Purpose of the Study:
- To investigate the complex phase diagram of 4'-n-pentylbiphenyl-4-carbonitrile (5CB) and ethanol mixtures.
- To determine the influence of water contamination on the phase separation behavior of these LC mixtures.
Main Methods:
- Polarizing microscopy with active cooling.
- Differential scanning calorimetry (DSC).
- Theoretical modeling to support experimental findings.
Main Results:
- A complex phase diagram for 5CB-ethanol mixtures was revealed, featuring a broad miscibility gap between isotropic phases.
- Phase separation occurs via spinodal decomposition or nucleation and growth.
- Water contamination dramatically increases the miscibility gap's temperature range, raising the critical temperature for spinodal decomposition from ~2°C to over 50°C with 3 vol% water.
Conclusions:
- Phase separation significantly impacts LC mixtures, affecting both equilibrium and non-equilibrium states.
- Water is a critical impurity that drastically alters the phase behavior of 5CB-ethanol mixtures.
- The study provides insights into controlling phase separation in LC systems through composition and contamination.
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