Chemical structures and compositions of all polymers were determined from 1 H-NMR spectra (JEOL 400MHz NMR spectrometer, Bruker UK Ltd., Coventry, UK). Samples for 1 H-NMR taken during polymerization were dried overnight in a vacuum oven to remove the solvent, then dissolved in 650 μL CDCl3. The weight percentage of DEAEMA and PEGMA were determined by calculating the integral ratio of the signal from the CH2 ethyl group next to N and closer to ester at 2.6 ppm, to that of the methoxy peak at 3.35 ppm.