1. Department of Physics, University of Ioannina, 451 10 Ioannina, Greece
2. Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
3. Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
4. University Research Center of Ioannina (URCI), Institute of Materials Science and Computing, 451 10 Ioannina, Greece