Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)
O 35.103: Poster
Dienstag, 27. März 2012, 18:15–21:45, Poster B
Contact size effects for the β-relaxation of PMMA using friction force microscopy — •Johannes Sondhauß1, Bernd Gotsmann2, Mark A. Lantz2, and André Schirmeisen3 — 1Institute of Physics, University of Münster, Germany — 2IBM Zurich Research Laboratory, Rüschlikon, Switzerland — 3Institute of Applied Physics, University of Giessen, Germany
The importance of polymer films for different technical applications brought increased attention to polymer surface studies. In addition polymers are an ideal model system for tribology due to their distinct modes of dissipation. The friction force microscope (FFM) has been recently proved useful to study surface processes in polymers. In this work we performed friction experiments using different Si-tips sliding on a PMMA film. We varied the applied load, the scan velocity and the sample temperature. In addition we used three different cantilevers with tip radii between 18 nm and 2.65 µm. Latter were produced by attaching a spherical Si-particle to the modified tip apex of a cantilever. Within the chosen parameter range we observed the β-relaxation as well as the onset of the α-relaxation and we were able to determine the activation energy of the β-relaxation for each of the data sets measured with the different tips. The observed activation energy increases for increasing tip radii.This trend seems to follow the Eyring model which describes the influence of the shear stress on the activation energy. Furthermore, a conversion of the scan velocity to frequency [1] allowed us to combine the individual data sets to one curve.
[1] Tocha et al., Soft Matter 5, 1489−1495 (2009)