Structure of Blue Phase III of Cholesteric Liquid Crystals

Abstract

We report large scale simulations of the blue phases of cholesteric liquid crystals. Our results suggest a structure for blue phase III, the blue fog, which has been the subject of a long debate in liquid crystal physics. We propose that blue phase III is an amorphous network of disclination lines, which is thermodynamically and kinetically stabilized over crystalline blue phases at intermediate chiralities. This amorphous network becomes ordered under an applied electric field, as seen in experiments.

On the effect of alignment layers on blue phase liquid crystals

“…In type-3 cells, without AL, no Bragg reflection in the visible range was found to be present for temperatures above 44. 5 C, whereas the cells with ALs possessed well defined Bragg reflection in the visible range at those temperatures. However, these cells do show platelet texture which is indicative of BP, e.g., reflecting in the UV region.…”

“…The results for the phase present above 44. 5 C in type-1 cell are shown in Figure 6. The switching on and off times are 364 ls and 167 ls, respectively.…”

“…BPIII is known to be an amorphous network of disclinations. 5 The lattice constant of the cube is determined by the radius of the DTC which in turn is dictated by the chiral pitch. The lattice constant of BPI is four times the diameter of the DTC (equal to the pitch), whereas for BPII it is two times the diameter of the DTC (equal to half of the pitch).…”

“…To understand the nature of the phase present above 44. 5 C, we analyzed the respective transmission spectra. In type-3 cells, without AL, no Bragg reflection in the visible range was found to be present for temperatures above 44.…”

Large Colloids in Cholesteric Liquid Crystals

“…However, these cylinders cannot be patched together in threedimensional space without introducing loci of defects referred to as disclination lines. Two phases in which the disclinations exhibit cubic symmetry have been identified experimentally (BPI and BPII) while a third (BPIII) is thought to be amorphous [16]. Recently, there have been significant advances in the technology of blue phases where polymer-stabilised formulations allow BPs to the used in a practically useful temperature range [8,19].…”