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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: Focus: Functional Polymer Hybrids I
CPP 20.2: Talk
Tuesday, March 8, 2016, 10:00–10:15, H51
Cooperative Photo-Switching in Nanofibers of Azobenzene Oligomers — •Stefan Kowarik1, Christopher Weber1, Manuel Gensler1, Tobias Liebig1, Anton Zykov1, Linus Pithan1, Jürgen P. Rabe1,3, Stefan Hecht2,3, and David Bléger2 — 1Department of Physics & — 2Department of Chemistry & — 3IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
The integration of molecular switches into hierarchical assemblies makes it possible to amplify a single-molecule mechanical photoresponse to macro-scale events involving many molecules. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be photo-switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via mechanical and electronic interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. Depending on the fraction of Z-azobenzene in the nanofibers the photoisomerization rate from the Z-isomer to the E-isomer is increased by more than a factor of 4. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency and amplifying molecular switching events with potential relevance for actuation and sensing.