Molecular origin of the ferroelectric nematic phase
In plain words
Some recently made liquid crystals line up with their electric dipoles all pointing the same way, which makes the fluid strongly polar, like a liquid ferroelectric. Which molecular features cause this is not understood.
Precise statement
Materials such as RM734 and DIO form a ferroelectric nematic phase $N_F$ with spontaneous polarization of about $2e4\,\mathrm{statC}/\mathrm{cm}^{2}$; in DIO it is preceded by an antiferroelectric modulated phase ($\mathrm{SmZ}_A$). Determine the molecular interactions (large longitudinal dipole of order $1e-17\,\mathrm{statC}\,\mathrm{cm}$, charge distribution along the molecule, steric shape) responsible for polar order, and give a criterion that predicts which molecular structures produce $N_F$ and the intermediate phase.
What would settle it
A molecular theory or simulation that predicts the presence or absence of $N_{\mathrm{F}}$ and its transition temperatures for a series of synthesized compounds before measurement.
Status in the literature
Unverified note
Landau-type and simulation models reproduce polar order for strongly dipolar molecules, but no predictive molecular criterion exists as of 2026.