For the last 5-10 years gelatine has been often used, beside the classical photographic applications, as an important component in Digital Imaging Applications. For both usages the stability of the gelatine/water gels (physical networks) is a key parameter during the production of imaging media. Therefore, the characterization of such systems is very important. By means of Analytical Ultracentrifugation a variety of different parameters can be measured, which are suitable to describe such gelled systems regarding thermodynamics and mechanical aspects. During this presentation it will be shown that the measurement of swelling pressures by means of Analytical Ultracentrifugation leads to the partial specific chemical potential of the solvent in the gel. These values are used to determine a so-called interaction parameter (according to Flory-Huggins-Staverman-van Santen), which indicates directly the thermodynamic stability of the system. Based on the presented data it becomes apparent that the system gelatine/water is very close to a miscibility gap and small variations of parameters like pressure or temperature may lead to a demixing into 2 new phases, which was found during the centrifugal measurements.
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