New examples of ferroelectric nematic materials showing evidence for the antiferroelectric smectic-Z phase

Journal Article · 22 February 2024 · Scientific Reports

DOI: https://doi.org/10.1038/s41598-024-54832-0 · OSTI ID:2311226

Nacke, Pierre; Manabe, Atsutaka; Klasen-Memmer, Melanie; Chen, Xi; Martinez, Vikina; Freychet, Guillaume; Zhernenkov, Mikhail; Maclennan, Joseph E.; Clark, Noel A.; Bremer, Matthias; Giesselmann, Frank

Abstract We present a new ferroelectric nematic material, 4-((4′-((trans)-5-ethyloxan-2-yl)-2′,3,5,6′-tetrafluoro-[1,1′-biphenyl]-4-yl)difluoromethoxy)-2,6-difluorobenzonitrile (AUUQU-2-N) and its higher homologues, the molecular structures of which include fluorinated building blocks, an oxane ring, and a terminal cyano group, all contributing to a large molecular dipole moment of about 12.5 D. We observed that AUUQU-2-N has three distinct liquid crystal phases, two of which were found to be polar phases with a spontaneous electric polarization P _s of up to 6 µC cm ^–2 . The highest temperature phase is a common enantiotropic nematic (N) exhibiting only field-induced polarization. The lowest-temperature, monotropic phase proved to be a new example of the ferroelectric nematic phase (N _F ), evidenced by a single-peak polarization reversal current response, a giant imaginary dielectric permittivity on the order of 10 ³ , and the absence of any smectic layer X-ray diffraction peaks. The ordinary nematic phase N and the ferroelectric nematic phase N _F are separated by an antiferroelectric liquid crystal phase which has low permittivity and a polarization reversal current exhibiting a characteristic double-peak response. In the polarizing light microscope, this antiferroelectric phase shows characteristic zig-zag defects, evidence of a layered structure. These observations suggest that this is another example of the recently discovered smectic Z _A (SmZ _A ) phase, having smectic layers with the molecular director parallel to the layer planes. The diffraction peaks from the smectic layering have not been observed to date but detailed 2D X-ray studies indicate the presence of additional short-range structures including smectic C-type correlations in all three phases—N, SmZ _A and N _F —which may shed new light on the understanding of polar and antipolar order in these phases.

• Sponsoring Organization: USDOE
• Grant/Contract Number: SC0012704
• OSTI ID: 2311226
• Alternate ID(s): OSTI ID: 2469569
• Journal Information: Scientific Reports, Journal Name: Scientific Reports Journal Issue: 1 Vol. 14; ISSN 2045-2322
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English