SEC was measured with a Waters Acquity APC system, equipped with Acquity Column Manager -S, Sample Manager -pFTN, Isocratic Solvent Manager, Acquity RI Detector and Aquity TUV Detector (Waters Corporation, Milford, MA, USA). The used columns are Acquity APC XT 45, 125 and 200. The eluent was dimethylformamide (DMF, Fisher Scientific, Vantaa, Finland) with a flow of 0.6 mL/min and at a temperature of 40 °C. The system was calibrated with poly(methyl methacrylate) (PMMA) standards (Polymer Standard Service, Agilent, Espoo, Finland). The data were analysed using Empower 3 and OriginPro (OriginLab Corporation, Northampton, MA, USA).