Structural Characterization of PDAPEI

The structure and average molecular weight (M_w) of PDAPEI were confirmed by Fourier Transform Infrared spectrometry (FTIR), ¹H-Nuclear Magnetic Resonance (¹H-NMR; Che et al., 2016 (link); Song et al., 2016 (link)), and Gel Permeation Chromatography (GPC). ¹H-NMR spectrum was obtained in DMSO-d₆ with 0.03% (v/v) tetramethylsilane (TMS) as internal standard using a Varian Mercury Plus 400 MHz spectrometer. FTIR spectrum was recorded in a KBr pellet using a Bruker Optics FTIR spectrometer. In GPC test, the M_w and polydispersity index (PDI) were obtained by an Agilent 1260 Infinity with a series of polyethylene glycol (PEG) standards and 25k Da PEI for calibration. The system was equipped with a diode array detector (DAD) and refractive index detector (RID) with two columns in a guard column and a PL aquagel-OH column at 40°C. As an eluent, 0.05% NaN₃ at a flow rate of 1.0 mL/min was used.