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| Freely suspended planar films of smectic liquid crystals have been made and widely studied since the mid 1970’s. In these films the smectic layering suppresses pore formation and stabilizes the film structure, such that films as thin as a single molecular layer can be maintained for extended periods. In addition to these planar films, freely suspended strands or filaments of discotic phases have also been made, in this case stabilized against undulations in filament diameter and rupture by the molecular columnal ordering. In principle, it should be possible to make such filaments out of smectic phases, with the layer ordering stabilizing the diameter. However, repeated efforts over the past 20 years have failed to produce stable smectic filaments in a broad range of smectic materials of rod-like molecules. Here we report the successful formation of stable smectic filaments in a fluid-layered liquid crystal phase of bent-core molecules, specifically in a 75:25 mixture of the compounds MHOBOW and NOBOW. Filaments from 5 to 50 microns in diameter and up to 2.5 mm in length have been stabilized for several hours in both the fluid smectic phase as well as in a crystalline phase. Using depolarized reflected light microscopy, the optic axis is observed to be parallel to the axis of the filaments, but in some cases a p reorientation of the optic axis is trapped in the filament and observed as the dark band as shown in the upper filament in the photograph (right). In an external electric field perpendicular to the axis of the filament, the p reorientation is squeezed to a narrow band that moves with constant velocity along the filament to one end. When the sign of the field is reversed the p reorientation moves to the other end of the filament. | ||
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