Emergent Ferroelectric Nematic and Heliconical Ferroelectric Nematic States in an Achiral "Straight" Polar Rod Mesogen

TL;DR

This paper reports the discovery of emergent ferroelectric nematic and heliconical states in an achiral straight polar rod mesogen, revealing novel phases and optical properties in ferroelectric liquid crystals.

Contribution

It introduces a new straight polar mesogen with unique ferroelectric nematic phases and demonstrates optical modulation using ultralow electric fields.

Findings

Discovery of ferroelectric nematic phase in straight polar molecules

Observation of exotic NF-HCNF-SmCF phase sequence

Reflective color modulation over VIS-NIR spectrum with ultralow E-field

Abstract

Ferroelectric nematic liquid crystals (NFLCs) are distinguished by their remarkable polarization characteristics and diverse physical phenomena, sparking significant interest and excitement within the scientific community. To date, over 150 NFLC molecules have been developed; however, there are no reports regarding straight linear polar molecules with a parallel alignment of the permanent dipole moment and the molecular axis. The straight polar mesogen nBOE exhibited an enantiotropic NF phase with a wide temperature window (up to 100 K) despite having a longer alkyl chain (up to n = 6) than the critical alkyl chain length of conventional models. Interestingly, nBOE with a medium length alkyl chain displayed an exotic phase sequence of NF-HCNF-SmCF during the elimination of positional displacement among adjacent molecules. Furthermore, we demonstrate the reflective color modulation of the HCNFLC over the entire VIS-NIR spectral regime by ultralow E-field (up to 0.14 V um^-1).