NMR Characterization of Polyethylene Glycol Conjugates for Nanoparticle Functionalization.

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