1. Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany; École Polytechnique Fédérale de Lausanne (EPFL), Institut des Matériaux, Laboratoire des Polymères, Bâtiment MX-D, CH-1015 Lausanne, Switzerland; and Department of Chemistry, CB# 3290, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290