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Updated: Jan 22, 2026
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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
6.8K
The Chiral Twist-Bend Nematic Phase (N*TB )
Rebecca Walker1, Damian Pociecha2, John M D Storey1
1Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen, AB24 3UE, UK.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|July 20, 2019
Summary
Chiral materials with a branched tail exhibit a twist-bend nematic (N*TB) phase. This chiral phase shows lower birefringence and higher transition temperatures than achiral counterparts, indicating chirality influences molecular ordering.
Area of Science:
- Materials Science
- Liquid Crystals
- Chirality Studies
Background:
- The twist-bend nematic (NTB) phase is a liquid crystal phase observed in specific molecular structures.
- Chirality, or 'handedness,' in molecules can significantly alter material properties.
- Understanding chiral effects on liquid crystal phases is crucial for developing new materials.
Purpose of the Study:
- To investigate the properties of the chiral twist-bend nematic (N*TB) phase.
- To compare the N*TB phase with the achiral NTB phase.
- To explore the influence of molecular chirality on liquid crystal phase behavior and transition temperatures.
Main Methods:
- Synthesis of chiral materials with a branched 2-methylbutyl terminal tail.
- Observation and characterization of liquid crystal phases using optical microscopy.
- Measurement of miscibility and transition temperatures with achiral liquid crystal analogs.
- Analysis of optical textures and birefringence.
Main Results:
- The chiral twist-bend nematic (N*TB) phase was successfully observed.
- Complete miscibility between the N*TB and achiral NTB phases was confirmed.
- The N*TB phase exhibited lower birefringence compared to the achiral NTB phase.
- Transition temperatures for chiral materials were higher than for racemic counterparts, suggesting chirality removes helical twist degeneracy.
- A square lattice pattern was observed in the N* phase above the N*TB-N transition.
Conclusions:
- Intrinsic molecular chirality removes the double degeneracy of helical twist sense in the twist-bend nematic phase.
- The observed lower birefringence in the N*TB phase suggests an additional averaging mechanism for molecular orientations.
- The higher transition temperatures indicate a significant impact of chirality on phase stability.
- The square lattice pattern may indicate a non-monotonic dependence of the bend elastic constant in the chiral N* phase.
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