J. Y. Josefowicz, N. C. Maliszewskyj, S. H. J. Idziak, P. A. Heiney, J. P. McCauley, Jr., and A. B. Smith, III, Science 260, 323-326 (1993).
Monolayer Langmuir-Blodgett films of a discotic mesogen have been studied with atomic force microcopy (AFM). These measurements confirm the "edge on" arrangement for the disk shaped molecules suggested by surface pressure-area isotherms, and show that the molecules form columns that are separated by 17.7 Angstroms +/- 10%. Column alignment is found to be predominantly along the film deposition direction, with an angular spread of 35 degrees. AFM images also show the mean disk separation within the columns to be 5.1 +/- 1.3 Angstroms, in good agreement with X-ray diffraction (XRD) results. Room temperature XRD on bulk samples of the same material indicates a disordered-hexagonal (Dhd) liquid crystalline mesophase, with a column-column spacing of 19.9 +/- 0.2 Angstrom.
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