1. CNRS, Université Bordeaux 1, Laboratoire de Chimie des Polymères Organiques, UMR 5629, 16, Avenue Pey Berland, 33607 Pessac Cedex, France, and Polymeric and Organic Materials Department, Graduate School of Science and Engineering, Tokyo Institute of Technology, H-127, 2-12-1, Ohokayama, Meguro-ku, Tokyo 152-8552, Japan