1. Institute of Polymers, Bulgarian Academy of Sciences, Akad. G. Bonchev St., Bl. 103-A, 1113 Sofia, Bulgaria
2. Center of Polymer and Carbon Materials, Polish Academy of Sciences, ul. M. Curie-Skłodowskiej 34, 41-819 Zabrze, Poland
3. Faculty of Applied Chemistry, Reutlingen University, Alteburgstraße 150, D-72762 Reutlingen, Germany