Unraveling the Dynamics of Nanoscopically Confined PVME in Thin Films of a Miscible PVME/PS Blend
Autor: | Sherif Madkour, Joerg Radnik, Paulina Szymoniak, Andreas Schönhals |
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Rok vydání: | 2017 |
Předmět: |
chemistry.chemical_classification
Materials science Relaxation (NMR) Analytical chemistry 02 engineering and technology Polymer Activation energy 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences chemistry.chemical_compound chemistry Free surface Electrode Polymer chemistry General Materials Science Polystyrene Thin film 0210 nano-technology Layer (electronics) |
Zdroj: | ACS applied materialsinterfaces. 9(42) |
ISSN: | 1944-8252 |
Popis: | Broadband dielectric spectroscopy (BDS) was employed to investigate the glassy dynamics of thin films (7-200 nm) of a poly(vinyl methyl ether) (PVME)/polystyrene (PS) blend (50:50 wt %). For BDS measurements, nanostructured capacitors (NSCs) were employed, where films are allowed a free surface. This method was applied for film thicknesses up to 36 nm. For thicker films, samples were prepared between crossed electrode capacitors (CECs). The relaxation spectra of the films showed multiple processes. The first process was assigned to the α-relaxation of a bulklike layer. For films measured by NSCs, the rates of α-relaxation were higher compared to those of the bulk blend. This behavior was related to the PVME-rich free surface layer at the polymer/air interface. The second process was observed for all films measured by CECs (process X) and the 36 nm film measured by NSCs (process X2). This process was assigned to fluctuations of constraint PVME segments by PS. Its activation energy was found to be thickness-dependent because of the evidenced thickness dependency of the compositional heterogeneity. Finally, a third process with an activated temperature dependence was observed for all films measured by NSCs (process X1). It resembled the molecular fluctuations in an adsorbed layer found for thin films of pure PVME, and thus, it is assigned accordingly. This process undergoes an extra confinement because of frozen adsorbed PS segments at the polymer/substrate interface. To our knowledge, this is the first example where confinement-induced changes were observed by BDS for blend thin films. |
Databáze: | OpenAIRE |
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