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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Synthesis and phase transitional behavior of dimer-like optically active liquid crystals.
Govindaswamy Shanker1, Channabasaveshwar V Yelamaggad
1Centre for Soft Matter Research , Prof. U. R. Rao Road, P. B. No. 1329, Jalahalli, Bangalore 560 013, India.
The Journal of Physical Chemistry. B
|August 12, 2011
Summary
Researchers synthesized novel optically active dimer-like mesogens with cholesterol cores. Even-parity compounds showed higher clearing temperatures, demonstrating an odd-even effect in liquid crystal properties.
Area of Science:
- Materials Science
- Organic Chemistry
- Liquid Crystals
Background:
- Low molar mass mesogens are crucial in advanced materials.
- Dimer-like liquid crystals offer unique structural and property variations.
- Cholesterol-based mesogens provide a chiral pro-mesogenic core.
Purpose of the Study:
- Synthesize and characterize novel optically active dimer-like mesogens.
- Investigate the correlation between molecular structure and liquid crystal phase behavior.
- Evaluate thermal, electrical switching, electrochemical, and gelation properties.
Main Methods:
- Synthesis of four homologous series of dimer-like mesogens.
- Thermal analysis using optical microscopy and differential scanning calorimetry.
- Structural characterization via X-ray diffraction.
- Evaluation of electrical switching, electrochemical, and gelation properties.
Main Results:
- Compounds exhibit various liquid crystal phases: chiral nematic (N*), twist grain boundary (TGB), chiral smectic A (SmA), and chiral smectic C (SmC*).
- Observed selective reflection in N* phases and ferroelectric behavior in SmC* phases.
- Phase behavior depends on spacer length/parity and terminal tail length.
- Prominent odd-even effect in clearing temperatures, with even-parity compounds showing higher values.
Conclusions:
- The synthesized low molar mass mesogens function analogously to liquid crystal dimers.
- Molecular structure, particularly spacer parity and tail length, significantly influences liquid crystal phase transitions.
- Demonstrated potential for selective reflection, ferroelectric behavior, electrochemistry, and gelation.
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