Switching and electrical properties of ferro‐ and antiferroelectric phases of MOPB(H)PBC

Abstract

Switching and dielectric relaxation phenomena were investigated for an antiferroelectric liquid crystal, 4,4-(1-methyloctyloxycarbonyl)phenyl]-49-[3-(butanoyloxy)prop-1-oxy]biphenyl carboxylate, exhibiting chiral smectic A (SmA*), smectic C (SmC*) and antiferroelectric (SmC A *) phases. Spontaneous polarisations, rotational viscosities, relaxation frequencies, dielectric strengths and distribution parameters were determined as a function of temperature. The electric field required for saturation of the spontaneous polarisation increased with a decrease in temperature. In the SmA* phase, only one relaxation mechanism was observed that behaves as soft mode. Two relaxation processes were detected in the SmC* phase. A high-frequency relaxation process invariant at 2.2 kHz was due to a Goldstone mode, but the origin of low-frequency relaxation process (1-20 Hz) is unclear; however, it may belong to an X-mode. The dielectric spectrum of the SmC A * phase exhibits two absorption peaks separated by two decades of frequency. The low-frequency peak is related to the antiferroelectric Goldstone mode, whereas the high-frequency peak originates from the anti-phase fluctuation of the directors in the anti-tilt pairs of the SmC A * phase.

Dielectric and switching properties of a highly tilted AFLC material (S)-(+)-4-(1-methylheptyloxycarbonyl)-2,3-difluorophenyl 4′-[3-(2,2,3,3,4,4,4-heptafluorobutoxy)prop-1-oxy]biphenyl-4-carboxylate

“…Rotational viscosity (γ ϕ ) has been estimated by using Equation (4), and the maximum value of γ ϕ is found to be 1.45 × 10 3 Pa/s. The value of γ ϕ increases with decrease in temperature similar to the other cases [51,52] where non-linear behaviour has been observed.…”

Dielectric Properties of Chiral Ferroelectric Liquid Crystalline Compounds with Three Aromatic Rings Connected by Ester Groups

“…Dielectric spectroscopy of ferroelectric systems provides a powerful insight into the dynamic aspects of these molecules which predetermine their applicability for different practical purposes [17][18][19][20][21][22]. In general, the observed spectra in the paraelectric (SmA*), ferroelectric (SmC*) and antiferroelectric (SmC* A ) phases of liquid crystals yield important information about collective processes as well as molecular modes [23][24][25][26][27][28][29]. The frequency dependent dielectric response in the orthogonal SmA* phase arises from the fluctuations of the director tilt (θ), commonly known as the soft mode (SM) [26,27].…”

High dielectric response of 2D-polyaniline nanoflake based epoxy nanocomposites

“…At low frequency, the decrease in the dielectric constant with increasing frequency is a general trend for most of the dielectric materials and it occurs due to electrode polarization capacitance. [32][33][34] The effect of electrode polarization capacitance is more noticeable for the materials having higher ionic conductivity. The ionic conductivity value will be discussed later.…”