Phasenverhalten von Polyelektrolyt Multilagen
Zusammenfassung der Projektergebnisse
The project aimed at improving the understanding of the phase behavior of polyelectrolyte multilayer (PEM) thin films. In this context, we investigated structural and mechanical properties of PEM films. To support the results of those methods we developed a calorimetric method allowing thin film measurements under humid conditions. For all investigations spray coating was optimized as common preparation, especially to coat the chip sensors for calorimetry. Different methods for the mechanical investigations were established as well as the needed characterization of the structural properties. Calorimetric investigations of thin films as PEM demanded the development of new methods. A thin film ac chip calorimeter in the frequency range of 1Hz...1000Hz for measurements down to 20 nm film thickness under controlled humidity was built up and its performance demonstrated. Several parameters turned out to be important for the mechanical properties of the PEM. Different linear charge densities and polyanion mixtures of variable mixing ratio show an influence. In both cases, it turned out that internal interactions are modified by changing the water content in the PEM. The water content change due to the relative humidity is an important parameter in variation of the film properties. The calorimetric investigations showed contrary to the suggestion of mechanical results no sign of a glass transition as it was expected from the large drop of elastic modulus. The combined results of mechanical and calorimetric investigations helped to clarify the question of the presumed glass-to-rubber transition in PEM as it was believed at the starting point of the project. As a final conclusion of the project we would not attribute the detected transition as a glass transition in classical sense.
Projektbezogene Publikationen (Auswahl)
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Neutron Reflectometry Study of Swelling of Polyelectrolyte Multilayers in Water Vapours: Influence of Charge Density of the Polycation. Langmuir (2009) 25, 11576-11585
R. Köhler, I. Dönch, P. Ott, A. Laschewsky, A. Fery, R. Krastev
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Phase transition in tetragonal hen egg-white lysozyme crystals. Applied Physics Letters (2009).95(26): 263702
A. V. Svanidze, H. Huth, S. G. Lushnikov, K. Seiji and C. Schick
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Cross-linkable polyelectrolyte multilayer films of tailored charge density. Chem. Mater. (2010) 22, 3223-3231
P. Ott, Patrick; J. Gensel, S. Roesler, K. Trenkenschuh, D. Andreeva, A. Laschewsky, A. Fery
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Free-Standing Membranes via Covalent Crosslinking of Polyelectrolyte Multilayers with Complementary Reactivity. Langmuir (2010) 26, 18182-18188
P. Ott, K. Trenkenschuh, J. Gensel, A. Fery, A. Laschewsky
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Tuning of the Elastic Modulus of Polyelectrolyte Multilayer Films built up from Polyanion Mixture. Macromolecules (2011) 44, 8954–8961
K. Trenkenschuh; J. Erath; V. Kuznetsov; J. Gensel; F. Boulmedais; P. Schaaf; G. Papastavrou; A Fery
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Study of phase transition in tetragonal lysozyme crystals by AC-nanocalorimetry. Thermochimica Acta (2012). 544(0): 33-37
A. V. Svanidze, H. Huth, S. G. Lushnikov and C. Schick
