We have reported two new series of compounds, nEC6F and nOEC3F, that show the ferroelectric nematic, NF, phase. We have determined that elongation of the terminal chain weakens the dipole-dipole interactions of the molecules along the director and thus lowers the temperature at which the axially polar NF phase is formed. For homologues of intermediate chain lengths, between the non-polar and ferroelectric nematic phases, another nematic phase emerges, Nx, having antiferroelectric character. The size of the antiparallel ferroelectric domains in Nx phase critically increases upon transition to the NF phase. In dielectric studies, both collective (‘ferroelectric’) and non-collective fluctuations are present, the ‘ferroelectric’ mode softens weakly at the N-NX phase transition because the polar order in this phase is weak. The transition to the NF phase is characterized by a much stronger lowering of the mode relaxation frequency and an increase in its strength, typical critical behaviour is observed.
The dataset includes:
1) publication in ACS Omega (manuscript and Supporting Information, pdf format ) - see also https://doi.org/10.1021/acsomega.3c05884
2) numerical data (ASCI) for optical birefringence measured vs. temperature for selected compounds
3) numerical data (ASCI) for dielectric permittivity measured vs. temperature and frequency for selected compounds
4) numerical data (ASCI) for periodicities determined by X-ray diffraction (XRD) and Resonant Soft X-ray Scattering (RSoXS) for selected compounds
5) Raw data for XRD and RSoXS experiments (2D detector images, in edf and fits formats)
