Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Electronic+Optical Properties
CPP 6.5: Vortrag
Montag, 25. Februar 2008, 15:00–15:15, C 230
Temperature dependent analysis of grating formation on azobenzene polymer films. — •Padmanabh Veer1, Ullrich Pietsch1, Paul Rochon2, and Marina Saphiannikova3 — 1Department of Solid State Physics, University of Siegen, ENC, 57068, Siegen, Germany — 2Department of Physics, Royal Military College, Kingston, Ontario, Canada K7K5L0 — 3Leibniz Institute of Polymer Research, 01069, Dresden, Germany
The temperature dependence of surface relief grating formation was studied using continuous and pulse like exposure. Surface relief gratings were inscribed on amorphous azobenzene polymer thin films using a holographic pattern of circularly polarized light at wavelength equal to 514 nm in a vacuum chamber to avoid the hot air turbulence and probed using a He-Ne laser of wavelength 633 nm by monitoring the first order diffraction peak (I1) as well as the specular reflected intensity (Is). Under continuous exposure permanent grating formation was observed up to a temperature of about 100 °C only. The same was found under pulse like exposure but grating still exists as long as the actinic light is on. Above 100 °C it relaxes entirely after switching the light off. Our findings can be interpreted by the competition between light-induced ordering of azobenzene side chains and temperature induced disorder. Because the accumulated stress within the polymer decreases with temperature, permanent grating formation can only be observed when the light-induced stress is above the yield stress. (Reference-Accepted Paper-P. veer1, U. Pietsch1, P. Rochon2, and M. Saphiannikova3 Molecular crystal and liquid crystal.)