The modern study of the liquid crystal (LC) phases formed by bent-core molecules [1] has led to many interesting and unexpected phenomena, including the first example of spontaneous reflection symmetry breaking and conglomerate formation in a bulk fluid phase.[2] Indeed, exploration of the unique behavior of bent-core materials is currently one of the most productive frontier research areas in soft matter science.[3] Perhaps the most complex of the known bent-core phases, the helical nanofilament (HNF) phase (also known as the B4 banana phase) has been under serious investigation since 1997,[1c, d] and continues to be a focus of interest in the bent-core materials constellation. Here, we report full characterization of the first example of a new phase in this family, HNF (mod), composed of simple alkoxybiphenylcarboxylate units and lacking the Schiff base groups found in previously known HNF mesogens.

The classic HNF phase possesses a unique hierarchical nanostructure: An assembly of twisted layers stacked to form well-defined chiral nanorods (individual HNFs ca. 40nm diameter), with a structure driven by intra-layer frustration leading to spontaneous saddle splay, and formation of layers with negative curvature.[4–6] Solid state NMR data suggest that within individual HNF layers the structure is crystalline,[7] though electron diffraction shows that no interlayer positional correlation exists.[4] The HNFs in turn form a kind of hexatic LC phase, which freezes into a glassy state at ca. 1108C. When the mesogens are achiral or racemic, an LC conglomerate of large heterochiral domains is easily seen in LC cells by polarized optical microscopy. The bulk HNF phase is porous,[4, 6] and when grown in the presence of other materials, can produce nanostructured composites.[8] Potential applications of the HNF phase and composites include nonlinear optics, organic electronics, photovoltaics, and chiral separations.