1. Zernike Institute for Advanced Materials; University of Groningen; Nijenborgh 4 Groningen 9747 AG The Netherlands
2. Chemistry Department and Institute for Polymer Technology; Wuppertal University; Gauss-Str. 20 D-42119 Wuppertal Germany
3. IBM Research - Zürich; Säumerstrasse 4 CH-8803 Rüschlikon Switzerland