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CPP: Chemische Physik und Polymerphysik

CPP 27: POSTER Polymer Physics and Materials

CPP 27.3: Poster

Donnerstag, 30. März 2006, 17:00–19:00, P2

Optical and mechanical anisotropy of oriented PET films studied by reflectance difference spectroscopy — •Klaus Schmidegg¹, Li Dong Sun¹, Günther Maier², Jozef Keckes², and Peter Zeppenfeld¹ — ¹Institut für Experimentalphysik, Johannes Kepler Universität Linz, Altenbergerstr. 69, A-4040 Linz — ²Erich Schmid Institut für Materialwissenschaften, Jahnstr. 12, A-8700 Leoben

A new method for the characterization of molecular orientation in polymers is presented, which is based on the determination of the optical anisotropy by reflectance difference spectroscopy (RDS). Its advantages are the sensitivity to birefringence, spectroscopic information, high time resolution and superior measurement precision as compared to refractive index measurements. The capabilities of RDS are presented for the special case of biaxially oriented poly(ethylene terephthalate) (PET) films, for which both magnitude and direction of the optical anisotropy can be determined. The data are consistent with refractive index measurements using spectroscopic ellipsometry and wide-angle X-ray scattering. The high time resolution and the simple setup enabled us to perform in-situ measurements during tensile testing of thin PET films. A clear correspondance of the initial optical and mechanical anisotropy directions can be seen. The RDS signal depends linearly on the applied strain and the gradient shows the same angular behavior. A closer look reveals that not only the size of the optical anisotropy changes, but also the position of the axes is rotated towards the drawing direction, which is a consequence of the reorientation of the molecules in the polymer.