Photoswitchable Merocyanine-Amphiphiles with Programmable Self-Assembly Times.

A merocyanine-based amphiphile was self-assembled into ellipsoids that can be disassembled by irradiation with visible light and reassemble in the dark after a delay of ∼70 minutes. Above a threshold concentration, the reassembly occurs when the ratio of protonated merocyanine to spiropyran reaches 7:3, suggesting both isomers are involved in the assembly. The thermal isomerization of the amphiphile when assembled (half-life ∼13 minutes) is significantly slower than that in dilute solution (half-life ∼3.6 minutes). The self-assembly behavior was confirmed by UV-vis spectroscopy, dynamic light scattering (DLS), small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). The delay between the isomerization and the assembly processes can be tuned between minutes and hours by adding differently charged co-surfactants.