1. Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; DSM Research, P.O. Box 18, 6160 MD, Geleen, The Netherlands; and State Key Laboratory of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 200051, P. R. China