1. Laboratoire de Chimie-Physique Macromoléculaire (LCPM), UMR CNRS-INPL 7568, Groupe ENSIC, 1 rue Grandville, B.P. 451, 54001 Nancy Cedex, France, and Laboratory of Polymeric and Composite Materials (LPCM), University of Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium