Regensburg 2013 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 16: Interfaces and Thin Films II (joint session with DECHEMA and VDI)
CPP 16.12: Talk
Tuesday, March 12, 2013, 12:45–13:00, H40
Azo-propellers as nanoscopic actuators in light-induced deformation of azobenzene polymer films — •Marina Saphiannikova1, Vladimir Toshchevikov1, and Jaroslav Ilnytskyi2 — 1Leibniz-Institut für Polymerforschung Dresden e.V. — 2Institute for Condensed Matter Physics, Lviv, Ukraine
We present the theoretical and MD simulation studies of thin azobenzene polymer films based on side-chain azo-oligomers having a stiff backbone and short spacers. Up to the glass transition temperature Tg the polymer backbone can be considered as a rigid prolate ellipsoid with a number of azobenzenes attached to it. Polar and azimuthal distributions of chromophores were studied at different temperatures and laser intensities. Their analysis was done in terms of nematic order parameters calculated in respect to the backbone. These parameters served then as input into a theoretical expression for the striction stress [1], which was found to be positive and above the yield stress. This explains irreversible elongation of the illuminated thin films below Tg, as found previously in experiment and MD simulations [2].
The light-induced reorientation of typical propeller-like structures is shown to be a microscopic reason of the sample elongation. Thus, molecular azo-propellers work as nanoscopic actuators which convert the light energy into material deformation. This finding opens a way for prediction of photomechanical properties of glassy azo-compounds directly from their chemical structure.
[1] V.Toshchevikov et al., J. Phys. Chem. B 113, 5032 (2009).
[2] J. Ilnytskyi et al., J. Chem. Phys. 135, 044901 (2011).