1. Laboratory of Polymer Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland; Department of Physical Sciences, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki, Finland; and Danish Polymer Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 423, DK-2800 Kgs. Lyngby, Denmark