Defect patterns of two-dimensional nematic liquid crystals in confinement

Abstract

A two-dimensional or quasi-two-dimensional nematic liquid crystal refers to a surface confined system. When such a system is further confined by external line boundaries or excluded from internal line boundaries, the nematic directors form a deformed texture that may display defect points or defect lines, for which winding numbers can be clearly defined. Here, a particular attention is paid to the case when the liquid crystal molecules prefer to form a boundary nematic texture in parallel to the wall surface (i.e., following the homogeneous boundary condition). A general theory, based on geometric argument, is presented for the relationship between the sum of all winding numbers in the system (the total winding number) and the type of confinement angles and curved segments. The conclusion is validated by comparing the theoretical defect rule with existing nematic textures observed experimentally and theoretically in recent years.

Network topology of interlocked chiral particles

“…We observe a variety of remarkable states at different packing fractions and L-axes lengths: at intermediate densities, the particles prefer interlocking with suppression of global orientational order, when both axes of the L-shape have comparable sizes. Otherwise the system tends towards a conventional nematic state [1,36,42]. At high packing fractions, the particles arrange in more rigid layers, which resembles a smectic-C structure.…”

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

“…The most prominent type of ordering, which is typically found in liquid crystals, is orientational (nematic) ordering, where the characteristically shaped subunits, i.e, molecules or colloidal particles in close proximity, show a tendency to align. If this preferred order gets frustrated, e.g., by confinement to a finite container [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49], constraining on a surface [50][51][52][53][54][55][56][57] or insertion of obstacles [58][59][60][61][62][63][64][65][66][67], topological defects emerge, which are discontinuities in the ordered structures that can display particlelike properties themselves [6,16,[68][69][70]. * Rene.Wittmann@hhu.de FIG.…”