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CPP: Chemische Physik und Polymerphysik

CPP 30: POSTER: Chemical physics

CPP 30.19: Poster

Dienstag, 8. März 2005, 16:30–18:30, Poster TU D

Photo- and thermo-induced aging of azobenzene layers — •Burkhard Stiller, Norman Mechau, Marina Saphiannikova, and Dieter Neher — University of Potsdam, Institute of Physics-Soft Matter Physics- Soft Matter Physics, Am Neuen Palais 10, 14469 Potsdam

We have studied the process of photo- and thermo-induced aging of thin azobenzene layers spin coated from tetrahydrofurane solution onto a glass substrate. The first cycle, when the film was either illuminated by visual light or annealed above the glass transition temperature, Tg, causes an abnormal hardening which manifests itself as an increase of elastic modulus of the layer. Additionally, diffusion of small dye molecules within the layer can be observed below Tg in the first heating cycle. In all subsequent cycles the layer shows a normal softening, whereas no diffusion below Tg can be observed. We ascribe the abnormal hardening in the first cycle to abrupt relaxation of excess free volume left in the layer by rapid solvent evaporation during spin coating process.