Dipolar interactions, molecular flexibility, and flexoelectricity in bent-core liquid crystals

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Bent-core molecules exhibit unique liquid crystal phases.
• Molecular flexibility and dipolar interactions significantly influence phase behavior.
• Understanding these effects is crucial for designing novel materials.

Purpose of the Study:

• Investigate the impact of dipolar interactions and molecular flexibility on bent-core molecular fluid structure and phase behavior.
• Explore the relationship between molecular geometry (bend angle) and observed liquid crystal phases.
• Calculate flexoelectric coefficients for nematic phases.

Main Methods:

• Utilized Monte Carlo computer simulations to model molecular interactions and phase transitions.
• Employed configurational-bias Monte Carlo simulations to study flexible molecular tails.
• Calculated flexoelectric coefficients using fluctuation relations.

Main Results:

• Linear molecules (gamma=0) showed isotropic, nematic, and smectic phases.
• Increasing bend angle (gamma > 20 degrees) eliminated untilted smectic phases and induced direct tilted smectic-isotropic transitions.
• Dipolar interactions reduced molecular inclination and destabilized nematic/untilted smectic phases.
• Molecular flexibility led to pronounced smectic layer fluctuations but minimal tilt.
• Flexoelectric coefficients were calculated for nematic phases.

Conclusions:

• Molecular geometry and electrostatic interactions are key determinants of bent-core liquid crystal phase behavior.
• Molecular flexibility enhances realism in simulations by introducing fluctuations but can reduce molecular tilt.
• Further computational effort is needed for reliable flexoelectric coefficient evaluation.