Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 63: Interfaces and Thin Films II (joint session CPP/DY, organized by CPP)
CPP 63.5: Vortrag
Freitag, 11. März 2016, 10:30–10:45, H51
Kinetic Monte Carlo Simulations of Photo-Switchable Molecules Tethered to a Surface — •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
Photo-switchable molecules can undergo a light-induced trans-cis isomerization. They can be used to build functional monolayers with light-controlled macroscopic properties. A recent experiment [1] showed that, in a monolayer densely covered with photo-switchable molecules, the relaxation of the induced birefringence follows a glasslike power-law dynamics. Furthermore, the relaxation can be efficiently fastened by illumination of the sample with circularly polarized light.
We developed a molecular model for the monolayer in which the trans and cis isomers are modeled as straight and bent needles, respectively. The needles are allowed to overlap and the system dynamics is generated by a kinetic Monte Carlo algorithm. We demonstrate that the glasslike power-law dynamics can be traced back to spatio-temporal correlations in the local structure of the system, i.e., to the formation of dynamical heterogeneities. Also, we find that the different degree of shape anisotropy of the two isomers has a significant effect on the system dynamics: the nearly isotropic cis isomers suppress the formation of extended dynamical domains. As a results, the relaxation is faster and follows a simple exponential decay.
[1] Fang, G. J., et al., Nature communications 4, 1521 (2013).