To analyse the resulting block copolymers by size exclusion chromatography (SEC), the DP 350, 20 wt% reaction mixtures was centrifuged, and the supernatant removed. The precipitate was diluted in THF. Copolymer samples were prepared as follow: the bioPISA suspension was centrifuged (13000 rpm) and the supernatant was removed. The sample was resuspended in 18 mL DI water, and the purification was repeated 4 times. The remaining residue was let to dry overnight at 40 °C and then suspended in 2 mL THF. The supernatant was passed through a 0.2 μm syringe filter (Whatman® Puradisc 13, PP) before analysis by THF SEC. SEC experiments were performed on an Agilent 1200 series HPLC system equipped with an Agilent PLgel mixed guard column (particle size= 5 µm) and two Agilent PLgel mixed-D columns (ID = 7.5 mm, L = 300 mm, particle size = 5 µm). Signals were recorded by a UV detector (Agilent 1200 series), an Optilab REX interferometric refractometer, and a miniDawn TREOS light scattering detector (Wyatt Technology Corp.). Samples were run using THF as the eluent at 30 °C and a flow rate of 1.0 mL min -1 . Data analyses were carried out on Astra software (Wyatt Technology Corp.) and molecular weights were determined based on narrow molecular weight polystyrene standards calibration (from 540 to 2'210'000 g mol ).