Ferroelectricity in a nematic liquid crystal under a direct current electric field

Abstract

We investigated the influence of the DC electric field on the electrical and optical properties of a liquid crystal compound 4-(4-nitrophenoxycarbonyl)phenyl 2,4-dimethoxybenzoate, known as RM734, exhibiting a ferroelectric nematic phase.

Polar nematic phases with enantiotropic ferro- and antiferroelectric behaviour

“…The N F phase is characterized with much higher electrical permittivity (650÷850) at low frequencies than other phases. However, the observed values are lower than those of RM734 25,56–58 but similar to the results obtained for DIO . 56 Unexpected electric response behaviour is noticed at the Iso–N phase transition where, despite the planar alignment, the electric permittivity increases ( ε ′ ∼ 450 at 1 kHz in N).…”

“…The ferroelectric domains are switchable by the AC and DC fields (Videos S2 and S3, ESI†), as was presented earlier for other compounds with the monotropic N F phase. 25,32,35 The optical studies confirm that the 3CN compound possesses the ferroelectric nematic phase in the heating cycle from the crystal phase (Fig. 3D and E).…”

“…The N F phase of the investigated compounds is characterized by the typical lens-shaped domain texture. 25,32 The domains of opposite polarity are separated by visible disclinations lines (Fig. 3C and I).…”

“…The uniqueness of polar nematic phases is associated with their extraordinary properties. The N F phase shows enormous dielectric permittivity, 16,20–24 significant spontaneous polarization, 25 elevated non-linear optical activity, 26–31 and electro-optical response with an exceptionally low or near-zero threshold voltage. 20,32–37 Additionally, both N F and N X phases are characterized by notable fluidity.…”

Lateral electric field switching in thin ferroelectric nematic liquid crystal cells

“…For a device with a particular alignment direction, often twisted domains are formed, 9–11 or two domains are observed in which the polarization is pointing in opposite directions. 22 However, it remains difficult to accurately control the creation and growth of polar domains (in a predefined way) by applying an electric field and the basic alignment. 10,23–25…”