Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

Abstract

Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

Interference of nonpolarized light in liquid crystal domains on a polymer surface

“…A capillary gap between the plates was ensured by 30-µm-thick teflon gaskets and filled with the 4-n-pentyl-4′-cyanobiphenyl (5CB) LC in the nematic phase. The orientation structure of the nematic in the cell was studied [13,18] on an Olympus BX51 polarization microscope (Japan). When necessary, an ac voltage with a frequency of 1 kHz was applied to the cell electrodes.…”

“…The pattern obtained in zero voltage is typical of a radial-planar nematic orientation, which is extended from the PC film deep in the layer by the coherence length ξ. Such a structure occurs whenever the LC thickness d exceeds the ξ value [12,14,18,19], even when the opposite cell surface was specially treated to form a homeotropic orientation. In the applied voltage U higher than the threshold value U th , at which the electric coherence length ξ E becomes equal to ξ [14], the texture acquires the form characteristic of a radial-homeotropic structure (Fig.…”

“…According to the configuration shown in Fig. 1, we express the components of the director n in the cylindrical coordinates: n ρ = -sinθ, n ϕ = 0, and n z = cosθ, where ϕ is the angle in the plane perpendicular to the z axis [18]. The standard free energy minimization procedure yields 2 2…”

Electric and Magnetic Field-Assisted Orientational Transitions in the Ensembles of Domains in a Nematic Liquid Crystal on the Polymer Surface

“…The domain network formed in the cells for few minutes [15]. Observations in the polarizing microscope showed that in the first-type cells there are areas of uniform planar alignment.…”

Optimized molecular structures of guest–host system for highly efficient coatable polarizer

“…In nematic liquid crystals, disclinations are observed as droplets-textures, thread-textures, or schlieren-textures in the boundary between an isotropic phase and a nematic phase [31][32]. The disclination shapes of the samples containing Host-006 are presented in Fig.…”