Light-Responsive Shape: From Micrometer-Long Nanocylinders to Compact Particles in Electrostatic Self-Assembly.

A light-triggered shape change of supramolecular nanostructures is achieved through electrostatically self-assembly of linear polyelectrolytes and oppositely charged dyes in aqueous solution: Upon UV-irradiation, 1-µm-long, flexible cylinders with a cross-section of 10 nm convert into ellipsoids of 400 nm × 40 nm. The nano-object shape is encoded in the molecular dye structure.