1. Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
2. Department of Physics, University of Ioannina, 45110 Ioannina, Greece, and Foundation for Research and Technology-Hellas, Biomedical Research Institute
3. Max-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany
4. Drittes Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany