Figure 1: Diastereomeric domains of a chiral guest mesogen infiltrated into left- and right-handed helical nanofilament networks of bent-core liquid crystal.

(a–c) Hierarchical self-assembly of achiral bent-core mesogens into helical nanofilaments (diameter, D∼30 nm). (d–f) A typical HNF sample is a conglomerate of independently nucleated left- and right-handed domains many hundreds of microns across, each of which is a network of homochiral helical nanofilament bundles that acts as a mesoscale porous chiral host. (e) Owing to their chirality, the surface patterning on nanofilaments that locally face each other within a domain have different orientations, which causes the director field of an achiral nematic liquid crystal in the pores to twist along a line between these boundary orientations. When the guest nematic is chiral, however, it has spontaneous bulk twist with a well-defined handedness. Since the boundary conditions presented by the parallel nanofilaments in each of the chiral HNF domains are mirror images, the average director orientation of a chiral nematic relative to the long axis of the nanofilaments is different (diastereomeric) in the two domains, and they display macroscopically distinct optical properties. (f) Typical cell texture in a mixture of NOBOW with a chiral guest material (in this case, 50% 7O.5* by weight). The helical nanofilaments phase-separate from the isotropic melt at ∼140 °C, nucleating at random sites in the cell surface and growing radially outwards to form homochiral, spherulitic domains with a local nematic-like texture of filaments (Supplementary Fig. 8). On average, we observe equal areas of left- and right-handed HNF domains in the cell. Scale bar, 100 μm. Unless otherwise specified, all cells used here were 3.2 μm thick. Schematic (a–c) is adapted from ref. 30.