Two mechanisms for the formation of the ferronematic phase studied by dielectric spectroscopy

Spontaneous mirror symmetry breaking and chiral segregation in the achiral ferronematic compound DIO

“…However, this phase, though identified as an ordinary nematic, has some unique dielectric properties such as exhibition of collective relaxation process. This was observed in the high-temperature nematic phase in both known ferronematic compounds DIO, 11,12 RM734 5 and its homologues. 7 The collective relaxation process is directly related to the polarity and it might thus be unique for ferronematic materials.…”

Three Distinct Polar Phases, Isotropic, Nematic, and Smectic-A Phases, Formed from a Fluoro-Substituted Dimeric Molecule with Large Dipole Moment

“…In some cases, the supercooling nature of the LC phase and the lower crystal melting temperatures are observed due to the fluorine-substituted molecules with weaker intermolecular forces . It is interesting to note that the N F phase as well as the SmAP F and Iso P phases are enantiotropic, giving a wide accessible temperature range while almost all N F phases reported are monotropic. − …”

“…A low-frequency (LF) mode is observed at 10–100 Hz in the N F , SmAP F and Iso P phases. The huge dielectric constants and low relaxation frequencies ( f r ) reveal that the LF mode is attributed to the collective fluctuation of polarization, which is typically observed in the ferroelectric phases. ,,,− ,− The dielectric spectra were analyzed by fitting with the following Cole–Cole equation ε * = ε ′ − i ε ″ = ε ∞ + normalΔ ε 1 + false( i ω τ false) 1 − α 0 < α < 1 where ω is the angular frequency, Δε (=ε s – ε ∞ ) is the dielectric strength, and ε s and ε ∞ are the “static-frequency” and “infinite-frequency” dielectric constants, respectively. τ = 1/(2π f r ) is the relaxation time (where f r is the relaxation frequency), and α is the distribution parameter of relaxation time.…”

“…Both materials reveal anomalously huge dielectric constant around 10,000 and a large spontaneous polarization ( P s ) of about 4 μC cm –2 , which are an order of magnitude higher than the previously reported values in other ferroelectric LC phases. Several other molecules and their ferroelectric properties are intensively studied. − …”

Electric field-induced interfacial instability in a ferroelectric nematic liquid crystal

“…RM734 and DIO have large molecular dipole moments of about 10 D, and a spontaneous polarization up to | | ~ 5 µC/cm 2 . The apparent dielectric permittivity and its anisotropy were reported to be orders of magnitude higher than those of classical nematics, reaching ~ 10 4 or higher 7 , 11 , 13 – 18 implying an extremely large sensitivity of the materials to electric fields. Such a large dielectric constant suggests a giant dielectrowetting at unprecedentedly low voltages, since its threshold scales with the square root of the fluid’s permittivity 19 – 21 .…”