TY - JOUR U1 - Wissenschaftlicher Artikel A1 - Früh, Johannes A1 - Rühm, Adrian A1 - He, Qiang A1 - Möhwald, Helmuth A1 - Krastev, Rumen A1 - Köhler, Ralf T1 - Elastic to plastic deformation in uniaxially stressed polylelectrolyte multilayer films JF - Langmuir / American Chemical Society : the ACS journal of surfaces and colloids N2 - Polyelectrolyte multilayer (PEM) are thin polymeric films produced by alternating adsorption of positively and negatively charged polyelectrolytes (PE) on a substrate. These films are considered drug delivery agents as well as coating material for implants, due to their antibiofouling and biologically benign properties. For these reasons the film mechanical properties as well as response to mechanical stress are important measurement parameters. Especially intriguing is the correlation of the mechanical properties of PEM on macroscopic level with the structure of PEM on molecular level, which is addressed here for the first time. This study investigates PEM from PDADMA/PSS produced by spraying technique with neutron and X-ray reflectometry. Reflectometry technique provides precise information on thickness and density (i.e., electron density or scattering length density, respectively), and, this way, allows to conclude on changes in film composition. Thus, neutron and X-ray reflectometry technique is suitable to investigate the overall and the internal transformations, which PEM films might undergo upon exposure to mechanical load. During uniaxial elongation two regimes of PEM deformation can be observed: An elastic regime at small elongations (below ca. 0.2%), which is characterized by a reversible change of film thickness, and a plastic regime with a permanent change above this limit. Both regimes have in common, that the mechanical load induces an increase of the film thickness, which is accompanied by an uptake of water from the surrounding atmosphere. The strain causes a molecular rearrangement within the PEM-structure of stratified layers, which, even in elastic regime, is permanent, although the thickness change remains reversible. Y1 - 2018 SN - 0743-7463 SS - 0743-7463 U6 - https://doi.org/10.1021/acs.langmuir.8b01296 DO - https://doi.org/10.1021/acs.langmuir.8b01296 VL - 34 IS - 40 SP - 11933 EP - 11942 S1 - 10 PB - American Chemical Society CY - Washington, DC ER -