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Broadband dielectric spectroscopy was applied to investigate the effect of gel-former agent on the dynamics of the collective modes in a ferroelectric liquid crystal mixture. In the investigated range of gel concentrations, the dynamics of the Goldstone mode is significantly reduced due to the formation of a hydrogen bonding network of the gel-former agent in ferroelectric liquid crystal. The observed changes in dynamics of the collective processes are sensitive to the history of the thermal treatment of the samples.

The effect of hydrophobic aerosil nanoparticles on the dynamics of the soft mode and the Goldstone mode near the SmA*–SmC* phase transition in the ferroelectric liquid crystal (S)-2-methylbutyl 4-n-nonanoyloxybiphenyl-4′-carboxylate has been investigated by means of broadband dielectric spectroscopy. The obtained results for hydrophobic aerosil composites exhibit some differences in the dynamics of the collective processes as compared with dielectric measurements for hydrophilic aerosil dispersions. The observed changes in dynamics of the collective modes near the SmA*–SmC* phase transition were explained taking into account differences in surface treatment of the aerosil nanoparticles and effect of random disorder.

Broadband dielectric spectroscopy was applied to investigate a newly synthesized antiferroelectric liquid crystal, (S)‐(+)‐4′‐(1‐methylheptyloxycarbonyl)biphenyl‐4‐yl 4‐(6‐heptanoyloxyhex‐1‐oxy)benzoate. Near the SmA–SmC* phase transition the soft and the Goldstone modes are observed. The temperature dependence of the soft mode dielectric strength follows the Cure–Weiss law. In a narrow range of temperature the collective and antiferroelectric relaxation modes coexist as a result of the competition between ferroelectric and antiferroelectric order in the successive smectic layers. In the antiferroelectric phase the low frequency, PL, and high frequency, PH, modes appear, which can be related to the in‐phase and anti‐phase azimuthal angle fluctuations of the director, respectively. The relaxation frequency of the PH and PL modes decreases linearly with decreasing temperature and satisfies the Arrhenius law. Some parameters involved in the extended Landau model of the SmA–SmC* phase transition could be obta...

On the basis of the extended Landau mean field model for the SmA—SmC* phase transition the temperature dependence of the dielectric strength and of the characteristic relaxation frequency of the soft mode are analyzed and some parameters involved in the free energy expansion are determined. The analogies and differences between the influence of the aerosil density and a dc electric field are shown.

Collective relaxation processes are completely undetectable in a ferroelectric liquid crystal confined in porous Anopore membranes, as a result of perfect orientation of the smectic layers perpendicular both to the long axis of the pores and the direction of the measuring electric field. In the ferroelectric liquid crystal – Anopore composite only one relaxation process, assigned to rotation of the molecule around the molecular short axis, appears throughout all smectic phases. The temperature dependence of the relaxation frequency and of the dielectric strength of this process also shows no irregularity at the point of polarization sign reversal. The temperature dependence of the relaxation frequency follows the Arrhenius law with an activation energy slightly higher in the ferroelectric SmC* phase. Analysis of the non‐linear changes of temperature dependence of the dielectric strength at the SmA–SmC* phase transition enables one to obtain the temperature dependence of the tilt angle of the molecules in ...

Dielectric spectroscopy was used to study the influence of random disorder in aerosil–ferroelectric liquid crystal dispersions on the dynamics of the Goldstone mode near the point of polarization sign reversal and the relaxation rate and dielectric strength of the collective modes. In general, the dielectric strength and the relaxation frequency of the Goldstone mode decrease, in comparison with the bulk, with increasing aerosil density near a point of polarization sign reversal. However, the characteristic frequency of the Goldstone mode varies with silica density in an opposite manner on each side of this point. This can be explained as a different sensitivity on the spatial confinement of different molecular conformers above and below the point of polarization sign reversal. The experimental results of temperature and frequency dependence of the complex dielectric constant are compared with predictions of the generalized Landau model for ferroelectric liquid crystals.

Broadband dielectric spectroscopy was applied to study the influence of the dispersed hydrophilic aerosil particle densities on the second-order smectic-A–smectic-C* phase transition and polarization sign reversal in the ferroelectric liquid crystal S-(−)-2-methylbutyl 4- n -nonanoyloxybiphenyl-4′-carboxylate. With increasing aerosil concentration the dielectric strength of the soft and the Goldstone mode considerably decreases and the complete disappearance of the Goldstone mode at ρ s = 0.20 g/cm 3 occurs along with significant broadening of the soft mode. The characteristic frequency of the Goldstone mode slightly increases with increasing density of the silica particles. The frequency degeneracy taking place in the smectic-A–smectic-C* phase transition is removed in the presence of aerosil and an increase in the frequency gap is observed. In a point of polarization sign reversal a rapid drop of the dielectric strength and the disappearance of the Goldstone mode was detected for bulk and confined ferroelectric liquid crystal. However, with increasing concentration of aerosil particles the dielectric strength of the Goldstone mode decreases as a function of temperature stronger below than above the sign reversal point. The characteristic frequency of the Goldstone mode below the point of polarization sign reversal decreases with increasing aerosil concentration.

The influence of the concentration of hydrophilic aerosil particles on the collective dynamic modes of the ferroelectric liquid crystal S‐(‐)‐2‐methylbutyl 4‐n‐nonanoyloxybiphenyl‐4′‐carboxylate near the SmA–SmC* phase transition is investigated by means of dielectric spectroscopy in the frequency range 10−2–107 Hz. For aerosil densities ρs = 0.025, 0.05, 0.08 and 0.15 g cm−3 considerable changes in the dielectric intensities of Goldstone and soft modes are observed. The characteristic frequency of the Goldstone mode slightly increases with increasing concentration of aerosil. The frequency degeneracy occurring in the SmA–SmC* phase transition is lifted in the presence of aerosil and an increase in the frequency gap is observed. Complete disappearance of the Goldstone mode at ρs = 0.20 g cm−3 occurs, along with significant broadening of the soft mode. The results are interpreted as an effect of structure, surface interactions and length scale of the helix in disordered confinement.