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Published on: February 7, 2017
Relationships between molecular structure and physical properties in bent-core mesogens
Wolfgang Weissflog1, H N Shreenivasa Murthy, Siegmar Diele
1Institut für Physikalische Chemie, Universität Halle-Wittenberg, Mühlpforte 1, 06108 Halle, Germany. weissflog@chemie.uni-halle.de
Summary
New bent-core mesogens with ester linkages exhibit diverse polar mesophases. Polar switching mechanisms include director rotation and collective molecular rotation, even in crystalline phases, offering novel electro-optical properties.
Area of Science:
- Materials Science
- Liquid Crystals
- Organic Chemistry
Background:
- Bent-core mesogens are a unique class of liquid crystals with potential applications in displays.
- Understanding the relationship between molecular structure and mesophase behavior is crucial for designing new materials.
Purpose of the Study:
- To synthesize and characterize novel five-ring bent-core mesogens with ester linkages and varying lateral substituents.
- To investigate the influence of lateral substituent position on mesophase behavior and electro-optical properties.
Main Methods:
- Synthesis of novel bent-core mesogens.
- Characterization using polarizing microscopy, differential scanning calorimetry, and X-ray diffraction.
- Electro-optical measurements to study switching mechanisms.
Main Results:
- Mesophase behavior strongly depends on the position of lateral substituents, leading to polymorphism including polar phases (SmAP, SmCP) alongside conventional smectic and nematic phases.
- Two distinct polar switching mechanisms were identified: director rotation and collective molecular rotation (field-induced switching of layer chirality).
- Remarkable polar switching was observed in crystalline phases of specific long-chain bent-core compounds, showing significant switching polarization.
Conclusions:
- The structural modifications of bent-core mesogens significantly impact their mesophase behavior and switching characteristics.
- Novel polar switching mechanisms, including field-induced chirality switching and switching in crystalline phases, have been demonstrated.
- These findings open new avenues for designing advanced liquid crystal materials with tunable electro-optical responses.
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