1. Laboratory of Polymer Chemistry and Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands, Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow 117912, Russia, and Department of Engineering Physics and Mathematics, Materials Physics Laboratory, Helsinki University of Technology, P.O. BOX 2200, FIN-02015 HUT, Espoo, Finland