1. Institute of Applied Chemistry, Riga Technical University, 3/7 Paul Walden Street, Riga LV-1048, Latvia
2. Institute of Solid State Physics, University of Latvia, 8 Kengaraga Street, Riga LV-1063, Latvia
3. Department of Polymer Chemistry and Technology, Kaunas University of Technology, K. Baršausko g. 59, Kaunas 51423, Lithuania