SEC was performed using 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). Acquity APC XT 45, 125 and 200 columns were used. 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 was analysed using Empower 3 and OriginPro (OriginLab Corporation, Northampton, MA, USA).