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Updated: Jul 13, 2026
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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Smectic-C*alpha phase with two coexistent helical pitch values and a first-order smectic-C*alpha to smectic-C*
1School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
Summary
This study reveals that the liquid crystal compound LN36 exhibits a standard chiral smectic phase sequence, not a reentrant transition. The SmC*alpha-SmC* transition is first-order, with unique observations of helical pitch behavior.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Liquid Crystal Physics
Background:
- Previous dielectric relaxation studies suggested a reentrant antiferroelectric-ferroelectric-antiferroelectric transition in LN36.
- Chiral smectic liquid crystals (Sm*) exhibit complex phase behaviors and transitions.
Purpose of the Study:
- To comprehensively investigate the phase transitions in the liquid crystal compound LN36.
- To clarify the nature of the phase sequence and transitions in LN36, particularly refuting previous reentrant transition claims.
Main Methods:
- Differential optical reflectivity
- Nonadiabatic scanning calorimetry
- Null transmission ellipsometry
- Resonant x-ray diffraction
Main Results:
- LN36 exhibits the typical chiral smectic phase sequence: SmA*-SmC*alpha-SmC*-SmC*FI1-SmC*A.
- The SmC*alpha-SmC* transition is confirmed as a first-order transition.
- A discontinuous change in helical pitch at the SmC*alpha-SmC* transition was observed.
- For the first time, two distinct helical pitch values were simultaneously observed just above the SmC*alpha-SmC* transition.
Conclusions:
- The compound LN36 does not display a reentrant antiferroelectric-ferroelectric-antiferroelectric transition.
- The observed phase sequence and first-order SmC*alpha-SmC* transition align with typical chiral smectic liquid crystal behavior.
- The simultaneous observation of dual helical pitches provides new insights into liquid crystal phase dynamics.
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