Flexoelectric polarization studies in bent-core nematic liquid crystals

Area of Science:

• Materials Science
• Condensed Matter Physics
• Liquid Crystal Physics

Background:

• Flexoelectric polarization (Pf) is a phenomenon in liquid crystals (LCs) arising from material deformation.
• Bent-core LCs exhibit unique molecular structures and properties compared to traditional calamitic LCs.
• Understanding flexoelectric effects in novel LC phases is crucial for advanced material applications.

Purpose of the Study:

• To measure the flexoelectric polarization (Pf) in four distinct bent-core nematic liquid crystal systems.
• To investigate the relationship between molecular structure, dipole moment, and flexoelectric coefficients.
• To compare the flexoelectric properties of bent-core LCs with those of calamitic LCs.

Main Methods:

• Utilized the pyroelectric effect to quantify flexoelectric polarization (Pf).
• Fabricated hybrid aligned nematic (HAN) cells for comprehensive pyroelectric response measurements.
• Measured the pyroelectric response across the entire nematic phase range.

Main Results:

• The magnitude of flexoelectric polarization (Pf) and the sum of flexoelectric coefficients (|e1+e3|) were found to be 3-6 times higher in the studied bent-core LCs compared to calamitic LCs.
• Flexoelectric polarization (Pf) demonstrated a dependence on the transverse dipole moment of the LC molecules.
• The sum of flexoelectric coefficients (|e1+e3|) was not as exceptionally large as previously reported values for |e3| alone in similar systems.

Conclusions:

• Bent-core liquid crystals exhibit significantly enhanced flexoelectric polarization compared to calamitic LCs.
• Molecular shape and the orientation of the dipole moment relative to the molecular axis are key factors influencing the sum of flexoelectric coefficients.
• The findings provide valuable insights into the flexoelectric behavior of bent-core LCs, relevant for developing new electro-optic materials.