LAUSR

Self-assembled chemical structures produce molecular aggregates with complex molecular functionalities often inspired by biological systems. But while self-assembly has been the focus of intense investigation, the disassembly of these molecular aggregates is much less explored, even though it can lead to temporal control over the aggregate functionality. Fredy et al. now describe artificial supramolecular tubules that disassemble in a nonlinear fashion, mimicking the disassembly dynamics of natural tubules. The system is composed of V-shaped molecules with two aromatic arms. Embedded in the chemical structure are also photoresponsive azobenzene groups. The molecules are made water-soluble by hydrophilic substituents. In water, the molecules self-assemble into tubules about 11 nm in diameter and more than 200 nm in length. Upon irradiation with UV light, the azobenzene groups switch to a nonplanar, cis configuration that induces mechanical strain to the tubules. With time, the aggregates first reorganize forming J-aggregates, in which the building blocks slide relative to each other, then break up into smaller tubules and finally disappear. The same experiment in a mixture of water and acetonitrile leads to simple, linear disassembly because the building blocks are more soluble in the organic solvent. The behaviour of these artificial tubules in water is not dissimilar to that of natural microtubules in which the disassembly is driven by an initial accumulation of strain energy. AM