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Nematic twist-bend phase with nanoscale modulation of molecular orientation.

Research paper by V V Borshch, Y-K YK Kim, J J Xiang, M M Gao, A A Jákli, V P VP Panov, J K JK Vij, C T CT Imrie, M G MG Tamba, G H GH Mehl, O D OD Lavrentovich

Indexed on: 06 Nov '13Published on: 06 Nov '13Published in: Nature communications



Abstract

A state of matter in which molecules show a long-range orientational order and no positional order is called a nematic liquid crystal. The best known and most widely used (for example, in modern displays) is the uniaxial nematic, with the rod-like molecules aligned along a single axis, called the director. When the molecules are chiral, the director twists in space, drawing a right-angle helicoid and remaining perpendicular to the helix axis; the structure is called a chiral nematic. Here using transmission electron and optical microscopy, we experimentally demonstrate a new nematic order, formed by achiral molecules, in which the director follows an oblique helicoid, maintaining a constant oblique angle with the helix axis and experiencing twist and bend. The oblique helicoids have a nanoscale pitch. The new twist-bend nematic represents a structural link between the uniaxial nematic (no tilt) and a chiral nematic (helicoids with right-angle tilt).