[1] Max Planck Inst Polymer Res, D-55128 Mainz, Germany
[2] Sofia Univ St Kliment Ochridski, Fac Phys, Opt & Spect Dept, Sofia 1164, Bulgaria
[3] Sony Deutschland GmbH, Mat Sci Lab, D-70327 Stuttgart, Germany
[4] Moscow MV Lomonosov State Univ, Dept Chem, Moscow 119899, Russia