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CPP: Chemische Physik und Polymerphysik

CPP 13: POSTER New Experimental Techniques

CPP 13.2: Poster

Dienstag, 28. März 2006, 17:00–19:00, P3

High sensitiv AC chip calorimetry for nanogram samples — •H. Huth, A. Minakov, and C. Schick — University of Rostock, Institute of Physics, Universitätsplatz 3, 18051 Rostock, Germany

The combination of silicon technology and calorimetry opens up new possibilities. Thin film calorimeter allow heating and cooling at rates up to 10.000 K/s. For several fast crystallizing polymers it is possible to prevent crystallization on cooling totally and to reach the amorphous glassy state. But often one would prefer to measure thermal properties of small samples at or at least close to thermodynamic equilibrium. This can be achieved by a combination of chip calorimetry and AC calorimetry at slow scanning or at constant bath temperature. The frequency chosen provides a well defined time scale of the experiment. A direct comparison with results from other dynamic methods like dielectric spectroscopy is possible. Based on a differential AC-calorimeter we show an improved experimental setup combining the advantages of the different methods already described. Not only a high sensitivity in the pico Joule per Kelvin range is achieved but AC measurements at relative high frequencies are possible too. As another application the combination of both methods is possible where one can prevent crystallization by very fast cooling before following of the crystallization at temperatures below the maximum crystallization temperature using the AC measurement technique. The AC technique allows the investigation of crystallization at very slow rates not easy achievable by fast scanning also in thin films of semicrystalline polymers. Measurements on small samples of semicrystalline polymers are presented.