Tuning Toroids

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Science  27 Oct 2006:
Vol. 314, Issue 5799, pp. 566
DOI: 10.1126/science.314.5799.566a

Amphiphilic molecules with rigid-rod cores can form structures such as tubules, ribbons, and vesicles in aqueous solution. These processes are driven largely by the burial of hydrophobic groups, but the final structures often depend on a balance of energetic and entropic effects.

Kim et al. have explored structures formed by dumbbell-shaped molecules with an aromatic core and distinct dendrimeric capping groups: on one end a hydrophilic oligoether and on the other a hydrophobic cluster of three alkyl chains, all either 6, 10, or 14 carbons in length. Transmission electron microscopy images show that these molecular building blocks form micelles. In particular, the hexyl-capped dumbbells form spheres and short cylinders, whereas those bearing decyl chains initially form curved cylinders that close to form toroids, a morphology that further isolates the hydrophobic cores. The compound capped by longer tetradecyl chains forms wider and more extended cylinders, a result that the authors attribute to a decrease in interfacial curvature relative to the decyl-capped species. — PDS

J. Am. Chem. Soc. 128, 10.1021/ja065487b (2006).

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