Manifestation of a Ferroelectric Phase Transition

Temperature dependences of the dielectric properties of ultrathin polyvinylidene fluoride films prepared using the Langmuir-Blodgett method were studied by linear and nonlinear dielectric spectroscopy. It is shown that ultrathin Langmuir films of polyvinylidene fluoride exhibit a manifestation of a first-order ferroelectric phase transition, which can be assigned to the interaction between the spontaneous polarization and the surfaces bounding the film. As the film thickness increases, the effect of the surfaces decreases and the ferroelectric phase transition shifts to high temperatures to vanish altogether when the temperature region of the transition rises above the melting point

Patterned-Liquid-Crystal for Novel Displays

The “Patterned-Liquid-Crystal for Novel Displays” is a Special Issue focused on new insights and explorations in the field of liquid crystals arranged in a periodic patterned way [...

Patterned-Liquid-Crystal for Novel Displays

The “Patterned-Liquid-Crystal for Novel Displays” is a Special Issue focused on new insights and explorations in the field of liquid crystals arranged in a periodic patterned way [...

Study of the vertically aligned in-plane switching liquid crystal mode in microscale periodic electric fields

The ongoing interest in fast liquid crystal (LC) modes stimulated by display technology and new applications has motivated us to study in detail the in-plane switching (IPS) vertically aligned (VA) mode. We have studied how the decrease of the period of the interdigitated electrodes (down to sub-micrometer scale) influences the switching speed, especially the LC relaxation to the initial homeotropic state. We have found that there are two types of the relaxation: a fast relaxation caused by the surface LC sub-layer deformed in the vicinity of the electrodes and the slower relaxation of the bulk LC. The speed of the fast (surface) mode is defined by half of a period of the electrode grating, while the relaxation time of the bulk depends on the LC layer thickness and the length of the driving electric pulses. Thus, the use of the surface mode and the reduction of the electrode grating period can result in significant increase of switching speed compared to the traditional LC modes, where the bulk relaxation dominates in electrooptical response. We have studied thoroughly the conditions defining the surface mode applicability. The numerical simulations are in good agreement with experimental measurements

Nematic liquid crystal alignment on subwavelength metal gratings

We have studied the alignment of a nematic liquid crystal (LC) material on aluminum subwavelength nanogratings as a function of the period, p, and the slit width to period ratio, w/p. A method, based on Fourier analysis of the transmittance spectra of the LC grating system, has been applied. We show that the gratings provide stable planar alignment only for shorter periods and narrower slits (p < 400 nm, w/p < 2/3). As these parameters increase, the homogeneous surface alignment changes to domains with different tilt angles or to spatially modulated alignment. We have also obtained a 90° twisted LC director distribution, implying sufficiently strong azimuthal LC anchoring at the grating surface