NMR Characterization of Polyethylene Glycol Conjugates for Nanoparticle Functionalization

[Image: see text] The molecular weight, purity, and functionalization of polyethylene glycols are often characterized by (1)H NMR spectroscopy. Oft-forgotten, the typical (1)H NMR pulse sequence is not (13)C decoupled. Hence, for large polymers, the (13)C coupled (1)H peaks arising from the repeating units have integrations comparable to that of the (1)H of the terminal groups. Ignoring this coupling leads to erroneous assignments. Once correctly assigned, these (13)C coupled (1)H 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 (1)H of the repeating unit.