1. Institute of Polymer Materials, Department of Materials Science, University Erlangen-Nürnberg, Martensstr. 7, D-91058 Erlangen, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany; Institute of Technical and Macromolecular Chemistry, University Hamburg, Bundesstr. 45, D-20146 Hamburg, Germany; and Institute of Mechanics, Technical University Darmstadt, Hochschulstr. 1, D-64289 Darmstadt, Germany