The Interfacial Dipole-to-Dipole Interaction as a Factor of Polar Anchoring in the Cells with Planar Liquid Crystal Alignment

Abstract

The frequency of dipole relaxation of liquid crystal (LC) layer at LC-solid interface, f r , is shown to be in full correlation with the polar anchoring energy W p ; the increase of W p is accompanied with the decrease of f r . This correlation is established by the use of the aligning polyimide layers treated with different methods. The anchoring energy increases and the relaxation frequency decreases in the following sequence of processes: rubbing-photoalignment-plasma beam alignment. The correlation between W p and f r is an evidence of strong contribution of dipole-to-dipole interaction at the LC-substrate interface to polar anchoring of LC. Based on this correlation new method of polar anchoring measurement can be developed.

Dielectric and electro-optical properties of solutions of chemically modified fullerene С60 in nematic liquid crystal

“…In the low-frequency area A (f < 100 Hz), observed is an essential (by orders) increase in ε′ and ε″ when the frequency decreases. As it was shown in [9], the presence of this part of the dielectric spectrum is caused by near-electrode phenomena. Properties of this layer will be analyzed after the analysis of bulk properties of the samples under study (part B of the dielectric spectrum).…”

“…These dependences between ε′ and ε″, according to theoretical representations, correspond to the Debye relaxation and are described by the equation (4). As shown in [9], the time for dipole polarization in the LC near-electrode layer is in inverse proportion to the conductivity of liquid. Therefore, for comparison of the data obtained when analyzing the near-electrode processes with the results summarized in Fig.…”

“…It follows from the work [9] that for planar oriented LC with positive anisotropy of dielectric permittivity (NLC corresponds to these characteristics), characteristic is the relaxation process caused by dipole polarization of molecules in a near-electrode layer. At low frequencies, almost all the voltage is applied to this layer of the sample, and an alternating current can be caused by oscillations of molecular dipoles within the angles that correspond to fluctuations of the order parameter.…”

“…It is this polarization that is responsible for appearance of the relaxation process inside the sample bulk. Our researches have shown [9] that, for nematic and isotropic phases of LC, the relaxation process caused by dipole polarization in a near-electrode layer is described by the Debye equation:…”

Multiferroic based on nematic liquid crystal and nanoparticles

“…As it was shown in [8], the relaxation process that occurs at f < 10 2 Hz can be explained on the basis of a two-layer Maxwell-Wagner polarization. In this case, one of the layers is a near-electrode section, in which for a given frequency band the charge transfer occurs due to fluctuations of dipoles of LC molecules within the angles corresponding to the fluctuations of the order parameter.…”