1. Department of Physics, University of Ioannina, 45110 Ioannina, Greece
2. Department of Chemistry, National and Kapodistrian University of Athens, 15771 Athens, Greece
3. Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), 45110 Ioannina, Greece
4. Max Planck Institute for Polymer Research, 55128 Mainz, Germany