Gel permeation chromatography (GPC) was performed on a Polymer Standard Service PSS (Mainz, Germany) system with following specifications: pump mod. 1260 infinity, MDS RIdetector mod. 1260 infinity (Agilent Technologies, Santa Clara, California, USA), precolumn: 50 x 8 mm PSS PFG linear M; 2 columns: 300 x 8 mm PSS PFG linear M (particle size 7 µm; pore size 0.1 -1.000 kg/mol) with hexafluoroisopropanol (HFIP, containing 3 g/L potassium trifluoroacetate (KTFA)) as eluent calibrated against PEG standards with molar masses from 0.1 g/mol to 1000 kg/mol. The columns were held at 40 °C and the flow rate was set to 0.7 mL/min. Prior to each measurement, samples were dissolved in eluent and filtered through 0.2 µm PTFE filters (Rotilabo, Karlsruhe, Germany) to remove particles, if any.