Structure and Morphology of Helicene Fibers

Nonracemic helicene 1 when cooled from the melt organizes itself into macroscopic liquid crystalline fibers. Transmission electron microscopic analysis shows that the fibers are comprised of lamellae 50−200 nm wide, each only ca. 10 nm high. Analyses by X-ray and electron diffraction demonstrate that the molecules are organized in hexagonally packed columns. Polarized light microscopy reveals that the columns are stacked so that their long axes parallel the long axes of the fibers. In ultrathin films, the alkyl side chains organize themselves further as in crystalline alkanes.