Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 1: Interfaces and Thin Films I
CPP 1.11: Vortrag
Montag, 26. März 2012, 12:30–12:45, C 130
Decelerating dewetting by shining light on a thin polymer film containing conjugated molecules — •Ioan Botiz1,2, Natalie Stingelin3, and Günter Reiter1,2 — 1Freiburg Research Institute for Advanced Studies — 2Institute of Physics, University of Freiburg — 3Imperial College London
We use an induced dewetting process as a method to control polymer conformations by stretching molecules within an ultrathin residual layer in the dewetting direction. Varying physical parameters like temperature, substrate type, light intensity, film thickness and age, we control the dewetting velocity, the final patterns (droplets and the residual thin layer), including the degree of molecular stretching. We show that, under nitrogen conditions, light intensity decelerates by two folds the dewetting velocity of a thin film of conjugated Poly[2-methoxy-5-((2'-ethylhexyl)oxy)-1,4-phenylenvinylene] (MEH-PPV) molecules embedded in an optically inert polystyrene matrix. No light effect is observed in thin films of polystyrene alone. Switching the light on and off leads to deceleration and acceleration of dewetting respectively, indicating a reversible effect of light. We attempt to explain our experimental observations suggesting that light induces new electronic states in MEH-PPV molecules (most probably long lived triplet states) leading to a change in molecular conformation characterized by a higher chain rigidity and therefore a higher polymer viscosity, i.e. lower dewetting velocity.