Thickness dependence of forming single crystal by liquid-crystalline blue phase on chemically patterned surface

Abstract

Topological defects of blue-phase liquid crystals (BPLCs) can be self-assembled into three-dimensional cubic crystalline structures, representing unique ordered states of matter among other liquid crystals. In a recent study, we presented the preparation of stable, macroscopic single-crystal blue phase materials by using chemically-patterned surfaces with binary anchoring and the appropriate geometry to favor a desired crystallographic orientation of the BPLC. Here we study the thickness dependence for chemically patterned surface for the crystal growth of the blue-phase II –which is characterized by a simple cubic crystalline structure, under a thermally controlled process. The hybrid cell used in our work to direct the self-assembly of the BP LCs has a top surface that provides uniform homeotropic anchoring, and a bottom surface with chemical patterns consisting of a stripe array of alternative planar and homeotropic anchoring. There is a spacer in between the two substrates to vary the cell thickness. Under such a process we achieve single crystals of blue-phase II with a [100]-lattice orientation (BPII[100]) that start to nuclei and grow from the pattern surface and propagate through the cell. By changing the cell thickness, we analyze the morphology difference of crystalline BPII[100] on the pattern surface.