To determine the degree of alkene functionalization (Fene) of HA-X, 1 H NMR spectrum of the polymer dissolved at 15 mg mL -1 in D2O was recorded. Peak area of the acetyl proton signal of HA at 1.97 ppm was compared to the corresponding alkene protons of the attached AE-, NB-or MA groups in the vinyl region (6.30-6.20 ppm). A more detailed description of the functionality calculation can be found in the supporting information.