1. Max Planck Institute for Polymer Research, 55128 Mainz, Germany
2. Institut für Chemie neuer Materialien, Universität Osnabrück, D-49069 Osnabrück, Germany
3. Department of Physics, University of Ioannina, 45110 Ioannina, Greece
4. Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), 45110 Ioannina, Greece