Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 25: Poster: Stress Relaxation in Polymers - From single molecules to biological cells (joint focus with BP)
CPP 25.5: Poster
Mittwoch, 28. März 2012, 11:00–13:00, Poster A
Changes in Structural and Wetting Properties of Polyelectrolyte Multilayers upon Mechanical Load — Johannes Früh1, Adrian Rühm2, Helmuth Möhwald1, Rumen Krastev3, and •Ralf Köhler4,5 — 1MPIKG Potsdam, Interfaces, 14424 Potsdam/Golm — 2MPIMR Stuttgart, ZWE FRM II, 85747 Garching — 3NMI at the University of Tübingen, Biomaterials, 72770 Reutlingen — 4TU Berlin, Stranski-Lab, 10623 Berlin — 5HZB, Soft Matter (F-I2), 14109 Berlin; Germany
Polyelectrolyte Multilayers (PEM) are formed by alternating adsorption of oppositely charged organic macromolecules onto a charged template. Despite big attempts for understanding the complex interactions in PEM and their subsequent effects, several major features are still unclear. This study addresses the mechanical properties of thin PEM films, with focus on the molecular changes upon lateral stress. Internal and overall restructuring is investigated using neutron and X-ray reflectivity, and UV-vis spectroscopy. An transition from elastic to plastic deformation is observed at an elongation of ca 0.2%. (A very tiny value which resembles the behaviour of solid bodies.) The transition is attended by, either a reversible, or an irreversible uptake of water from the ambient atmosphere. A superstructure created by selective replacing of PSS with deuterated PSS in the PSS/PDADMAC-multilayer showed gradual and irreversible degradation of the layer structure upon elongation. Decoiling of entangled polymer chains which, in extra, are strongly interacting via ionic bonds is considered as the origin of the molecular intermixing upon mechanical load.