1. Laboratory for Polymer Research, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium
2. Institute of Nuclear Science, Rijksuniversiteit Gent, Proeftuinstraat 68, B 9000 Gent, Belgium
3. Polymer Materials Research Group, Department of Organic Chemistry, University of Gent, Krijgslaan 281, S4-bis, B-9000 Gent, Belgium
4. Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic
5. Central Michigan University, Department of Physics, Mt. Pleasant, Michigan 48859