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Viscoelastic properties are one of the most fundamental properties of chiral liquid crystals. In general, their determination is not a straightforward task. The main problem is the multitude of physical parameters needed to determine the value of the elasticity and viscosity constants. It is also necessary to consider the character of a respective phase. This problem is particularly important in the case of chiral phases such as ferroelectric and antiferroelectric phases or in the blue phases. There are several experimental methods to measure viscosity and elasticity constants in chiral phases. These methods use various phenomena to detect deformation, e.g., light transmission, polarization current, light modulation, dielectric constant and helix deformation or helix unwinding. Commonly, an external electric field is used to induce deformation, the homogeneity of which inside the cell is essential. This study is focused on the analysis of the effect of laser photobleaching on the electro-optic properties of the antiferroelectric liquid crystal and on the homogeneity of the electric field. The results obtained by confocal microscopy as a function of the cell depth are presented. The influence of the stabilization procedure of the isolated region performed by controlled laser photobleaching on the electro-optic properties has been studied. The observation was conducted using a polarizing microscope, and numerical analysis of two-dimensional colored textures was performed. The obtained results suggest that laser photobleaching can produce an anchoring effect, which has a positive effect on the electro-optic properties of antiferroelectric liquid crystal. [ABSTRACT FROM AUTHOR]

Abstract Physical properties of new binary mixture of two ferroelectric liquid crystalline compounds, regarding the properties of the components, were studied. It turned out that both components and the mixture exhibit the ferroelectric smectic C* phase in a wide temperature range. Moreover, the calorimetric, texture observations as well as dielectric studies revealed an additional monotropic liquid crystalline phase for one of the mixture component, which was identified, based on X–ray diffraction results, as tilted one with hexagonal order within the layers. Dielectric spectroscopy has shown the strong low frequency relaxation process in the SmC* identified as related to Goldstone mode based on the mean–field model. Additionally, the molecular reorientation around the short axis was recognized in the monotropic hexatic phase. The temperature dependencies of the spontaneous polarization and switching time for new binary mixture and its components were compared and analyzed in terms for possible applications. Graphical abstract Unlabelled Image Highlights • Orienting polymer layer influence on molecular dynamics is studied by FDDS. • X-ray diffraction for identification of liquid crystalline phases is used. • DSC and POM was used to study thermal stability. • Parameters important for applications are designed. [ABSTRACT FROM AUTHOR]

The aim of our study was to analyze the influence of various concentrations of γ-Fe2O3 nanoparticles on the physical properties of the liquid crystalline ferroelectric SmC* phase, as well as to check the effect of introducing nanoparticles in the LC matrix on their properties in the prepared five nanocomposites. UV-vis spectroscopy showed that the admixture reduced the absorption of nanocomposites in the UV range, additional absorption bands appeared, and all nanocomposites were transparent in the range of 500–850 nm. The molecular dynamics in particular phases of the nanocomposites were investigated by the dielectric spectroscopy method, and it was found that nanoparticles caused a significant increase in the dielectric constant at low frequencies, a strong modification of the dielectric processes in the SmC* phase, and the emergence of new relaxation processes for the highest dopant concentrations. SQUID magnetometry allowed us to determine the magnetic nature of the nanoparticles used, and to show that the blocked state of nanoparticles was preserved in nanocomposites (hysteresis loops were also registered in the ferroelectric SmC* phase). The dependence of the coercive field on the admixture concentration and the widening of the hysteresis loop in nanocomposites in relation to pure nanoparticles were also found. In turn, the FT-MIR spectroscopy method was used to check the influence of the impurity concentration on the formation/disappearance or modification of the absorption bands, and the modification of both the FWHM and the maximum positions for the four selected vibrations in the MIR range, as well as the discontinuous behavior of these parameters at the phase transitions, were found. [ABSTRACT FROM AUTHOR]

The aim of this paper is to show, by systematic studies, the influence of γ-Fe2O3 nanoparticles on the physical parameters of the liquid crystalline matrix, exhibiting a ferroelectric phase in a wide temperature range. The detailed research was carried out by using diffraction (PXRD), microscopic (OM, SEM, FCPM, POM), thermal (DSC), optical (TLI), electric and spectroscopic (FTIR) methods. We show that even the smallest concentration of γ-Fe2O3 nanoparticles largely modifies the parameters of the ferroelectric SmC* phase, such as spontaneous polarization, switching time, tilt angle, rotational viscosity, dispersion anchoring energy coefficient and helix pitch. The admixture also causes a significant reduction in the temperature of phase transitions, broadening the SmA* phase at the expense of the SmC* phase and strong streaking of the texture. We present and explain the non-monotonic modification of these parameters with an increase in the nanoparticle concentration. The influence of oleic acid admixture on these parameters is also widely discussed. We have shown that certain parameters of organic-metal nanocomposites can be controlled by the appropriate amount of metal admixture. [ABSTRACT FROM AUTHOR]