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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
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Driving a Liquid Crystal Phase Transition Using a Photochromic Hydrazone
Mark J Moran1, Mitchell Magrini2, David M Walba2
1Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States.
Journal of the American Chemical Society
|October 9, 2018
Summary
Researchers developed a new chiral dopant for liquid crystals (LCs). This dopant enables light-controlled self-assembly, leading to tunable optical properties and a novel light-gated optical window.
Area of Science:
- Soft Matter Physics
- Materials Science
- Organic Chemistry
Background:
- Dynamic manipulation of soft matter properties is key for adaptive functional materials.
- Liquid crystals (LCs) exhibit tunable photophysical properties based on their self-assembly.
- Controlling LC self-assembly with external stimuli is crucial for advanced applications.
Purpose of the Study:
- To design and synthesize a novel chiral dopant for nematic liquid crystals.
- To investigate the light-induced control over LC self-assembly and photophysical properties.
- To demonstrate a light-gated optical window based on light-induced phase transitions in LCs.
Main Methods:
- Synthesis of a new chiral dopant featuring an isosorbide scaffold and bistable hydrazone-based light switches.
- Doping nematic liquid crystals (5CB) with the synthesized chiral dopant.
- Photoisomerization of the dopant using specific wavelengths of light (e.g., blue light).
- Characterization of LC phase behavior and photophysical properties using techniques like optical microscopy and spectroscopy.
Main Results:
- The chiral dopant successfully controlled the self-assembly and photophysical properties of nematic LCs.
- Bistability of the light switches allowed for kinetic trapping of various helical assemblies, reflecting different wavelengths.
- Irradiation with blue light induced an isothermal phase transition from cholesteric to smectic A* phase in doped 5CB.
- This phase transition enabled modulation of LC film transparency, creating a light-gated optical window.
Conclusions:
- A novel chiral dopant based on light-switchable units offers precise control over LC self-assembly and optical properties.
- The demonstrated isothermal phase transition provides a new mechanism for light-responsive materials.
- The developed light-gated optical window has potential applications in adaptive displays and smart windows.
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