Regensburg 2019 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 2: Responsive and Adaptive Systems (joint session CPP/DY)

DY 2.9: Vortrag

Montag, 1. April 2019, 11:45–12:00, H8

Columnar clusters of three-arm azobenzene stars - MD simulations of a light-induced phase transition — •Markus Koch1, Marina Saphiannikova1, Svetlana Santer2, and Olga Guskova11Institute Theory of Polymers, IPF Dresden, Germany — 2Institute of Physics and Astronomy, University of Potsdam, Germany

In this study we investigate star-shaped molecules consisting of a central benzenetricarboxamide (BTA) core and three symmetrically attached azobenzene groups. In aqueous solution these molecules exhibit a distinctive photoresponsive self-assembly behavior. In the absence of light or exposed to blue visible light they form long fibrous structures. When irradiated with UV light the columns disassemble but can be restored after resuming exposure to the initial conditions [1]. This phase transition is a result of the trans-cis photoisomerization of the centrally anchored azobenzene arms. We demonstrate, using DFT and MD simulations, that the solvophilicity of azo stars increases with the number of azo groups present in the cis state [2]. Further on using MD simulations, the stability of the columnar clusters in water is tested, while again varying the amount of trans and cis arms per molecule. Our results indicate that clusters with a large fraction of cis-arms display higher disorder or may even break apart. Lastly, also the kinetics of cluster self-assembly from random initial distributions is studied.

We gratefully acknowledge support from the German Research Foundation (DFG), projects GU 1510/3-1 and SA 1657/13-1.

[1] Lee, S. et al. Langmuir 29 (19), 5869 (2013)

[2] Koch, M. et al. J. Phys. Chem. B 121, 8854 (2017)

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