1. Laboratory of Polymer Chemistry, Department of Materials; Swiss Federal Institute of Technology, ETH Zürich, HCI J 541; Wolfgang Pauli Strasse 10 8093 Zürich Switzerland
2. Nanotechnology Group; ETH Zürich, Säumerstrasse 4 CH-8803 Rüschlikon Switzerland
3. Laboratory for Surface Science and Technology; Department of Materials, ETH Zurich and Dipartimento di Scienze Chimiche e Geologiche of Università di Cagliari; 09100 Cagliari Italy