1. Maurice Morton Institute of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, Institut für Makromolekulare Chemie, Universität Hannover, Am Kleinen Felde 30, 30167 Hannover, Germany, and Départment de chimie and CERSIM, Université Laval, Quebéc, Quebéc, Canada G1K 7P4