Characterization of PEG-PPS copolymers. (A) GPC-MALS characterization of PPS-COOH (red), H2N-PEG-COOH (blue), and cPEG-PPS (green). The cPEG-PPS sample displayed a population of polymers with peak elution time at ~9 min, corresponding to Mn = 7.32 kDa (see Table 1), in addition to excess unreacted H2N-PEG-COOH. (B) FT-IR spectra of the same three polymer samples confirm the formation of the copolymer. The appearance of the 1700-1630 cm-1 peak and disappearance of the 1650-1590 cm-1 free amine bending peak in the copolymer versus the unreacted PEG is consistent with the formation of an amide linkage between the N-terminus of the PEG block and the C-terminus of the PPS block. (C) UV-Vis absorbance of cPEG-PPS (red) versus the post-dialyzed ssDNA-PEG-PPS conjugates (green, blue) confirms the conjugation of ssDNA to the polymers, as referenced by the characteristic peak at 260 nm.