Director configurations in nematic droplets with inhomogeneous boundary conditions

Abstract

The nematic droplets with director configurations intermediate between the bipolar and radial structures have been investigated experimentally and theoretically. The liquid crystal 4'-n-pentyl-4-cyanobiphenyl (5CB) with a variable addition of the lecithin dispersed in polyvinylbutyral has been used. The characteristic textures of the droplets formed at various lecithin contents have been examined using polarizing microscope both in the crossed polarizers and without analyzer. The computer simulation has been performed for proper ordering of the director in spherical nematic droplets by minimizing the free energy in the one-constant approximation. The inhomogeneous boundary conditions with strong anchoring of the molecules at the interface have been used. The distribution of the anchoring angle at the droplet surface has been estimated based on analysis of observed patterns. The simulated textures of the droplets under crossed polarizers are shown to compare well with the experimental ones.

The influence of electric field-induced orientation on the retraction of a liquid crystal droplet immersed in a flexible polymer matrix

“…In fact, the textures shown in Fig. 3 are very similar to the simulation results for LC droplets with distorted axial configuration, which proves the reorientation of director in the electric field in our experiments [28].…”

Director configurations in nematic droplets with tilted surface anchoring

“…Being observed without analyzer the interface is practically invisible where the director is aligned perpendicular to the light polarization because n  np. And vice versa, it is sharply seen where the director is parallel to the polarizer orientation [19][20]. Thus, the comprehensive analysis of the optical textures in both crossed polarizers [1,21] and without analyzer allows determining the director distribution within the droplet.…”

“…The tilted anchoring was realized within liquid matrix in the certain temperature range at the constant concentration of surfactant [7] or for the certain range of surfactant concentration [16]. In PDLC films the resultant director orientation at the interface depends on the droplet size [9], the length of lateral alkyl chains of polymer macromolecules [12], the temperature [17], the variation of curing agent of photo-curable polymer [18], the surfactant content in polymer matrix or LC [19,20].…”

Beyond displays: The recent progress of liquid crystals for bio/chemical detections

“…Instead of forming planar LC-aqueous interface, LCs can be emulsified to form LC droplets [53][54][55][56][57][58][59][60][61][62][63]. Nematic 5CB in liquid form at room temperature again becomes a good choice of making LC droplets/emulsions.…”