1. Université de Bordeaux, Centre de Recherche Paul Pascal - CNRS, Avenue Schweitzer, 33600 Pessac, France, Department of Chemical & Biomolecular Engineering, Department of Chemistry, The Smalley Institute for Nanoscale Science & Technology, Rice University, 6100 Main St. Houston, Texas 77005, and Group Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands