Polymerization Goes Tubular

By taking advantage of a polyether macrocycle’s tendency to stack upon itself, chemists have assembled a new type of nanotube using addition polymerization (J. Am. Chem. Soc., DOI: 10.1021/ja209792f). Because the tubes are prepared via organic synthesis, it’s possible to introduce structural variations tailored for specific applications, note Joseph W. Lauher, Te-Jung Hsu, and Frank W. Fowler of the State University of New York, Stony Brook, who came up with the novel nanotube. To build the structures, the researchers first prepared a 34-atom polyether macrocycle with two parallel diacetylene units. The macrocycles stack to form two crystalline polymorphs, one of which has 4.84-Å spacings between molecules. The ideal spacing for addition polymerization to occur is only slightly longer—4.9 Å—and indeed, the researchers found that upon annealing at 40 °C for 35 days, the stacked macrocycles polymerized into nanotubes. The nanotubes are the first example of a structurally characterized tubular addition polymer, the researchers point out, and they provide a general strategy for synthesizing other tubular polymers.