1. Laboratoire de Physico-chimie Macromoléculaire, Université Pierre et Marie Curie, CNRS URA 278, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France, and Department of Chemical Engineering, University of Patras and Institute of Chemical Engineering and High Temperature Chemical Processes, ICE/HT-FORTH, P.O. Box 1414, GR-26500, Patras, Greece