P. Henderson, D. Beyer, U. Jonas, O. Karthaus, H. Ringsdorf, P. A. Heiney, N. C. Maliszewskyj, S. S. Ghosh, O. Y. Mindyuk, and J. Y. Josefowicz, J. Am. Chem. Soc. 119 4740-4748 (1997).
We have used pressure-area isotherms, x-ray diffraction, atomic force microscopy, and infrared dichroism to study Langmuir and Langmuir-Blodgett films of 2,3,6,7,10,11-hexaalkoxytriphenylenes which were selectively di- and tri-functionalized with CnH2n-OH groups at the 2,3-, 2,6-, 3,6- and 3,6,10- positions. The bulk phase behavior of these compounds was also established using polarizing microscopy and differential scanning calorimetry. At the air-water interface, the hydroxy groups make contact with the water, and the Langmuir film stability is strongly correlated with proximity of the hydroxy groups on the molecule. Mixtures of the 2,3- and 3,6- isomers display a dramatic increase of the liquid-crystalline mesophase temperature range compared to the pure compounds. The mixtures also have lower molecule areas at the air-water interface and produce thin films with a complex superlattice structure of disk tilts, showing for the first time the ability of triphenylene isomer alloys to self-organize.