1. CNRS, Univ. Bordeaux, Centre de Recherche Paul Pascal, UMR 5031, 115 Avenue Schweitzer, 33600 Pessac, France
2. Univ. Bordeaux, CNRS, Bordeaux INP, Laboratoire de Chimie des Polymères Organiques, UMR 5629, F-33600, Pessac, France
3. Department of Physics, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway