To Be or Not To Be Polar: The Ferroelectric and Antiferroelectric Nematic Phases
Ewan Cruickshank, Paulina Rybak, Magdalena Majewska, Shona J. Ramsay, Cheng Wang, Chenhui Zhu, Rebecca Walker, John M. D. Storey, Corrie T. Imrie, Ewa Górecka, Damian Pociecha
Abstract
High Resolution Image Download MS PowerPoint Slide We report two new series of compounds that show the ferroelectric nematic, N F, phase in which the terminal chain length is varied. The longer the terminal chain, the weaker the dipole–dipole interactions of the molecules are along the director and thus the lower the temperature at which the axially polar N F phase is formed. For homologues of intermediate chain lengths, between the non-polar and ferroelectric nematic phases, a wide temperature range nematic phase emerges with antiferroelectric character. The size of the antiparallel ferroelectric domains critically increases upon transition to the N F phase. In dielectric studies, both collective (“ferroelectric”) and non-collective fluctuations are present, and the “ferroelectric” mode softens weakly at the N–N X phase transition because the polar order in this phase is weak. The transition to the N F phase is characterized by a much stronger lowering of the mode relaxation frequency and an increase in its strength, and a typical critical behavior is observed.