NMR Characterization of Polyethylene Glycol Conjugates for Nanoparticle Functionalization

The molecular weight, purity, and functionalization of polyethylene glycols are often characterized by ¹H NMR spectroscopy. Oft-forgotten, the typical ¹H NMR pulse sequence is not ¹³C decoupled. Hence, for large polymers, the ¹³C coupled ¹H peaks arising from the repeating units have integrations comparable to that of the ¹H of the terminal groups. Ignoring this coupling leads to erroneous assignments. Once correctly assigned, these ¹³C coupled ¹H peaks can be used to determine both the molecular weight of the polymer and the efficacy of conjugation of a terminal moiety more accurately than the uncoupled ¹H of the repeating unit.