Molecular models for ferroelectric liquid crystals with conventional and anomalously weak layer contraction

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• The ferroelectric smectic C* phase exhibits complex behavior influenced by molecular structure and interactions.
• Understanding the relationship between molecular chirality, polarity, and macroscopic properties is crucial for developing advanced materials.

Purpose of the Study:

• To develop a molecular theory for the ferroelectric smectic C* phase.
• To investigate the influence of molecular chirality and dipole interactions on phase behavior.
• To model spontaneous polarization, molecular tilt, and layer spacing as functions of temperature.

Main Methods:

• A simple molecular model incorporating a uniaxial core and off-center dipoles.
• A general effective potential to describe core interactions.
• Numerical calculations of polarization, tilt, and layer spacing.
• Analysis of the ferroelectric smectic C* phase, including transitions influenced by biaxial order parameters.

Main Results:

• The molecular theory successfully models the ferroelectric smectic C* phase.
• Calculated polarization variations generally deviate from tilt angle variations.
• This deviation is more pronounced in materials with low layer contraction, aligning with experimental data.
• The model qualitatively reproduces experimental data for polarization, tilt, and layer spacing in mixtures with varying layer contraction.

Conclusions:

• The developed molecular theory provides a robust framework for understanding ferroelectric smectic C* materials.
• The model highlights the distinct temperature dependencies of polarization and tilt.
• It accurately captures the behavior of materials with conventional and anomalously weak layer contraction.