Figure 1.

Synthesis and characterization of SPEI600. (a) Schematic illustration of synthesis of SPEI600. (b) ¹H-NMR spectra of SPEI in CDCl₃. The chemical shift δ0.9 ppm is assigned to the proton –CH₃ on stearic acid backbone (marked for a); δ2.5–2.93 ppm are assigned to the proton –NCH₂CH₂N– protons of the PEI backbone (marked for e, f, g, h, i, j, k, l and m); δ1.24 ppm is assigned to the proton (CH₂)₁₄ on PEI backbone (marked for b); δ1.58 ppm and δ2.13–2.17 ppm are assigned to the proton –COCH₂CH₂– on stearic acid (marked for c and d); and δ2.93–3.3 ppm are assigned to the proton –CONHCH₂– on PEI backbone (marked for n and o).