Berlin 2015 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 22: Interfaces and Thin Films III (joint session with CPP)
DS 22.8: Vortrag
Mittwoch, 18. März 2015, 11:30–11:45, C 243
Monte Carlo Simulations for Switchable Model Molecules — •Raffaele Tavarone1, Patrick Charbonneau2, and Holger Stark1 — 1Institut für Theoretische Physik, Technische Universität Berlin, D-10623 Berlin, Germany — 2Departments of Chemistry and Physics, Duke University, Durham, North Carolina 27708, USA
Light-switchable molecules are chemical compounds that can undergo a light-induced, reversible trans-cis isomerization. They can be used to build functional monolayers with, for example, switchable wetting properties. A typical example of a light-driven trans-cis transition is the azobenzene isomerization.
Inspired by the conformational changes of the azobenzene compound, we build a model in which a trans isomer is regarded as a straight needle while a cis isomer is regarded as a bent needle. First, we determine the phase behavior of such molecules on a planar surface using Monte Carlo simulations. The resulting phase diagram (density versus molecular shape) shows several liquid-crystal mesophases.
Second, we build a kinetic model for a glassy monolayer inspired by a recent experiment [1]. They showed that the spontaneous algebraic relaxation of orientational order, inscribed in the sample with linearly polarized light, is strongly enhanced by illumination with circularly polarized light. In our simulations we allow molecules to switch between the trans and cis isomers due to the interaction with light. We are able to trace the influence of neighbors hindrance and other microscopic processes on the kinetic of the relaxation reported in the experiment.
[1] Fang, G. J., et al., Nature communications 4, 1521 (2013).