Difference in the interaction of nano-diameter rod and tubular particles with a disclination line in a nematic liquid crystal

The liquid crystal forces generated by nanowires and nanotubes are different due to their heterotopicity for the liquid crystal director.

Quaternions and hybrid nematic disclinations

Disclination lines in nematic liquid crystals can exist in different geometric conformations, characterized by their director profile. In certain confined colloidal suspensions and even more prominently in chiral nematics, the director profile may vary along the disclination line. We construct a robust geometric decomposition of director profile in closed disclination loops and use it to apply topological classification to linked loops with arbitrary variation of the profile, generalizing the self-linking number description of disclination loops with the winding number . The description bridges the gap between the known abstract classification scheme derived from homotopy theory and the observable local features of disclinations, allowing application of said theory to structures that occur in practice.

Liquid crystal alignment in cylindrical microcapillaries

A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

Topological transformations on the droplets in chiral nematic liquid crystals with developed electroconvection

The dynamics and transformations of defects in chiral nematic droplets P in the electric field are studied experimentally, as function of the ratio of the droplet radius R to the helix pitch P. It is shown that, depending on the R/P ratio and the applied voltage, various orientation-structural transformations can be realized. In particular, for the ratio R/P<1 only droplets with one destroyed boojum are observed. The application of an a.c. electric voltage causes the latter to rotate. In the case of R/P~1, the dynamics of the rotation of the disclination line is transform into a periodic decay of the boojum (with a topological index S=1) into two surface defects. In the case R/P>1, a process of merging two surface defects with a topological index 1/2 into a bulk defect of the ”hedgehog“ type with S=1 is observed. The mechanisms of the observed processes are discussed.