| Chirality, the lack of reflection symmetry, at the molecular level has a profound influence on the ordering of molecular assemblages at the macroscopic scale. The role of chirality will be discussed in two examples. First is the self-assembly of filamentary structures, with strands of molecules wrapped around each other in a helical manner, cue to chirality. These grow to a certain diameter, with increasingly tilted and bent filaments as diameter increases. At a critical diameter internal strains prevent further growth in diameter, while growth in length is unchecked. Second is the self-assembly of monolayers of rod-like fd virus particles, with the virus particles oriented on the average perpendicular to the plane of the layer, like a single layer of a smectic-A liquid crystal. Because these virus particles are chiral, they would prefer a twisted packing, which is incompatible with the layer structure. The twisted packing can only appear locally, at layer edges or in isolated defects in the interior of the layer. As chirality increases, the twisted regions achieve lower energy, until they can drive remarkable transformations to structures with longer edges and/or a greater number of defects. |