Solid–Liquid Crystal Biphasic Ferroelectrics with Tunable Biferroelectricity

Abstract

Ferroelectricity has been separately found in numerous solid and liquid crystal materials since its first discovery in 1920. However, a single material with biferroelectricity existing in both solid and liquid crystal phases is very rare, and the regulation of biferroelectricity has never been studied. Here, solid–liquid crystal biphasic ferroelectrics, cholestanyl 4‐X‐benzoate (4X‐CB, X = Cl, Br, and I), which exhibits biferroelectricity in both the solid and liquid crystal phases, is presented. It is noted that the ferroelectric liquid crystal phase of 4X‐CB is a cholesteric one, distinct from the ordinary chiral smectic ferroelectric liquid crystal phase. Moreover, 4X‐CB shows solid–solid and solid–liquid crystal phase transitions, of which the transition temperatures gradually increase from Cl to Br to I substitution. The spontaneous polarization (Ps) of 4X‐CB in both solid and liquid crystal phases can also be regulated by different halogen substitutions, where the 4Br‐CB has the optimal Ps because of the larger molecular dipole moment. To the authors’ knowledge, 4X‐CB is the first ferroelectric with tunable biferroelectricity, which offers a feasible case for the performance optimization of solid–liquid crystal biphasic ferroelectrics.

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