1. Department of Polymer Science & Engineering, Lund Institute of Technology, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden; Flemish Institute for Technological Research (Vito), Boeretang 200, B-2400 Mol, Belgium; and Centre for Surface Chemistry and Catalysis, Faculty of Applied Bioscience and Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, B-3001 Leuven, Belgium