Made to Order Even More

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Science  24 Jan 2003:
Vol. 299, Issue 5606, pp. 477
DOI: 10.1126/science.299.5606.477a

In smectic-phase liquid crystals, rodlike molecules tend to pack parallel to one another in a layered structure. When a semifluorinated chain is attached near the middle of a rodlike aromatic molecule with polar endgroups, a smectic phase can still form, with the molecules lying flat in the layers. Prehm et al. show that if instead a branched chain that bears both fluorinated and hydrocarbon branches is added, additional ordering occurs to create a two-dimensional lattice. Upon cooling from the isotropic melt, indications of a columnar structure were observed in both polarized light microscopy images and x-ray diffraction patterns. Ordering between adjacent layers appears to be caused by the separation of the perfluorinated and linear hydrocarbon units, which prefer to pack with like units only. Analysis of the small-angle x-ray reflections indicated that the secondary packing leads to a noncentered rectangular lattice. — MSL

J. Am. Chem. Soc. 10.1021/ja0289999 (2002).

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