Aggregation structure of chiral cubic liquid crystals revealed by X-ray diffraction utilizing a new algorithm

Abstract

Chiral aggregation structure spontaneously formed by achiral rodlike molecules, a long-time unsolved problem in liquid crystal science has been clarified by applying a new crystallographic algorithm recently developed while utilizing...

Room-temperature Ia3̄d phase obtained for the binary mixture containing different sizes of siloxanyl terminals

“…3 Investigation of the M-30 mixture after being aged at 296 K for the indicated periods: (a) DSC phase behaviors on cooling (1C) from the melt (top) and on heating (bottom four) and XRD patterns in the (b) small-angle and (c) wide-angle ranges, and (d) microphotographs under crossed polarizers (the brightness of all the frames i-iv was by 80% increased by using image software than their original frames taken on the POM observation). I2 1 3 indicates the ''Im % 3m'' type chiral Cub phase, 16 although the POM observation could not detect the chirality.…”

“…1a), 13 while breaking of such balance (spontaneous mirror symmetry breaking) would produce chiral cubic phases. [14][15][16] The formation mechanism and stability of the structures are still not well clarified. In the case of LC nano-structures constructed by seemingly rod-like molecules, the helical network formation originates from the packing frustration caused by the side-by-side arrangement of antispindle-shaped molecules (Fig.…”

“…This indicates a too largely expanded shape of the terminal chain for the formation of the Ia% 3d Cub phase, thus alternatively producing those Col phases at those temperatures. Another interesting observation for the compound, however, is that not the achiral Ia % 3d but a chiral Cub phase of ''Im% 3m'' type is formed below and around room temperature, the reason for which remains unclear at this stage (Hereafter, the chiral Cub phase is abbreviated I2 1 3 because the space group has been proposed as the most reasonable one by us very recently, 16 although it was a subject of debate. 14,[28][29][30] ).…”