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Influence of multilayer nanostructures on photoisomerization and photoorientation of azobenzene

: Jung, B.-D.; Stumpe, J.; Hong, J.-D.


Thin solid films 441 (2003), Nr.1-2, S.261-270
ISSN: 0040-6090
Fraunhofer IAP ()

Based on the layer-by-layer electrostatic deposition method, we have realized alternating multilayer systems of polyelectrolytes with an internal order via using membrane-forming polyionenes that contain rigid azobenzene chromophores linked to flexible alkylene spacers. The photoisomerization and photoreorientation of azobenzene moieties in the multilayer assemblies were investigated in dependence on nanostructures that were formed with varying spacer length of the polyionene. In combination with spectroscopic behavior, both molecular photoreaction and light-induced reorientation processes are used as probes to characterize order and dynamics of the multilayer assemblies. Increasing the spacer length from 6 to 10, 12 carbons results in a strong aggregation of polyionene in solution that again gives rise to a dense packing of the chromophores in the multilayer assemblies on a solid substrate. The supramolecular order influences kinetics of trans–cis photo-isomerization and reorientation of the azobenzene moieties under the action of linearly polarized light. In particular, the different irradiation conditions (wavelength, power density, polarization direction) have a significant influence on the photo-induced anisotropy.