1. Laboratory of Polymer Chemistry, Process Development Group, and Department of Inorganic Chemistry and Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, Chemical Physics Department, University of Groningen, Nijenborgh 4, 9747 AG Groningen, and Dutch Polymer Institute, P.O. Box 902, 5600 AX Eindhoven, The Netherlands