1. Netherlands Organisation of Scientific Research NWO, Dutch Belgian Beamline, European Synchrotron Radiation Facility, B. P. 220, 38043 Grenoble, France; Department of Physical and Colloidal Chemistry, Free University of Brussels, Pleinlaan 2, 1050 Brussels, Belgium; and Laboratory of Polymer Technology and Laboratory of Polymer Chemistry, Eindhoven University of Technology TUE, P.O. Box 513, 5600 MB Eindhoven, The Netherlands