6 Materialchemie
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The composition of the surface layer in dependence from the distance of the polymer/air interface in thin films with thicknesses below 100 nm of miscible polymer blends in a spatial region of a few nanometers is not investigated completely. Here, thin films of the blend poly vinyl methyl ether) (PVME)/polystyrene (PS) with a composition of 25/75 wt% are investigated by Energy Resolved X-ray Photoelectron Spectroscopy (ER-XPS) at a synchrotron storage ring using excitation energies lower than 1 keV. By changing the energy of the photons the information depth is varied in the range from ca. 1 nm to 10 nm. Therefore, the PVME concentration could be estimated in dependence from the distance of the polymer/air interface for film thicknesses below 100 nm. Firstly, as expected for increasing information depth the PVME concentration decreases. Secondly, it was found that the PVME concentration at the surface has a complicated dependence on the film thickness. It increases with decreasing film thickness until 30 nm where a maximum is reached. For smaller film thicknesses the PVME concentration decreases. A simplified layer model is used to calculate the effective PVME concentration in the different spatial regions of the surface layer.
Polymers at interfaces play a major role in a broad variety of applications ranging from engineering purposes (for instance polymer based nanocomposites) to high tech implications (for instance light emitting diodes). Here the glass transition and glassy dynamics is considered for epoxy-based nanocomposite with Layered Double Hydroxide nanofiller and for thin films of a misicble polymer blend of PVME/PS with thicknesses down to 7 nm. The materials are investigated by spectroscopic techniques (broadband and specific heat spectroscopy), as well as by fast scanning calorimetry and small- and wide-angle X-ray scattering.