Design Principles for Fluid Molecular Ferroelectrics.

Area of Science:

• Soft condensed matter physics
• Organic materials science
• Molecular engineering

Background:

• Fluid molecular ferroelectrics combine ferroelectricity with 3D fluidity, retaining spontaneous polarization.
• Predicting ferroelectric phase (nematic or smectic order) in fluid molecular materials is a key challenge.
• Understanding structure-property relationships is crucial for designing functional polar fluids.

Purpose of the Study:

• To establish design principles for fluid molecular ferroelectrics.
• To develop a predictive framework for engineering ferroelectric fluid phases.
• To investigate the role of molecular structure, specifically hydrogen-fluorine substitution, on ferroelectric ordering.

Main Methods:

• Synthesis of 45 systematically varied organic molecules.
• Analogy to solid molecular ferroelectrics for design principles.
• Large-scale, fully atomistic molecular dynamics simulations.

Main Results:

• Subtle hydrogen-fluorine substitutions enable tuneable syn-parallel pairing motifs.
• Specific pairings lead to geometrically constrained lamellar ferroelectric order.
• Diversified pairings stabilize nematic ferroelectric ordering.
• Smectic ferroelectricity emerges from discrete lateral pairing modes.
• Nematic phases arise from multiple equivalent polar configurations.

Conclusions:

• Experimentally validated design principles for fluid molecular ferroelectrics are established.
• A predictive framework for engineering functional polar fluids is provided.
• Molecular design, particularly H/F substitution, controls ferroelectric phase and order.