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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Interfaces and Thin Films III (joint session CPP, DS)

CPP 37.8: 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).