Surface-imaging of frozen blue phases in a discotic liquid crystal with atomic force microscopy

Discotic cholesteric phases with extremely small pitches were obtained with cellobiose derivatives as chiral dopants. These binary mixtures lend to form up to three distinct blue phases. An interesting property of these mixtures is that the blue phases can be supercooled to a glass-like state. Microscopic studies, reflection spectra, and Kossel diagrams all indicate that the three discotic blue phases BPDI, BPDII and BPDIII are analogous to the well-known calamitic modifications. In addition to the optical studies, we investigated the free surfaces of the frozen blue phases using atomic force microscopy.