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O: Fachverband Oberflächenphysik

O 26: Organic, Polymeric, and Biomolecular Films II

O 26.2: Talk

Tuesday, March 27, 2007, 11:30–11:45, H42

Cooling rate dependence of the glass transition of poly(propylene glycol) — •Simone Streit¹, Christian Gutt², and Metin Tolan¹ — ¹Fachbereich Physik, Universität Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund, Germany — ²Deutsches Elektronen Synchrotron (HASYLAB), Notkestr. 85, 22607 Hamburg, Germany

We performed in-situ x-ray reflectivity measurements to determine the cooling rate dependent freezing of capillary waves on the polymer melt poly(propylene glycol) (PPG). Only above the glass transition temperature T_G the surface roughness σ can be described by the capillary wave model for simple liquids, whereas the surface fluctuations are frozen in at lower temperatures. As the state of a glass forming liquid strongly depends on its thermal history, this effect occurs for fast cooling rates already at higher T than for slow cooling. For the fastest cooling rates an astonishingly high shift of T_G up to around 240 K compared to the bulk value of 196 K could be observed.