PROTON NMR CHARACTERIZATION OF POLY(ETHYLENE GLYCOLS) AND DERIVATIVES

Derivatives of poly(ethylene glycol) (PEG) are of importance in a variety of applications. Often it is difficult to determine the identity of the end groups and the purity of these derivatives. In the present work we show that proton NMR spectra of PEGs dissolved in deuterated dimethyl sulfoxide (but not other solvents) reveal a hydroxyl peak at 4.56 (±0.02) ppm, which does not shift or broaden with variation in concentration of the PEG, water, or impurities and which is well separated from the large backbone resonance. The hydroxyl resonance in other solvents does not show this independence, and thus it is difficult to locate and utilize. The PEG hydroxyl resonance for samples in dimethyl sulfoxide is, therefore, well suited for quantifying percent substitution and molecular weight of PEG and derivatives. Use of this method is illustrated. © 1990, American Chemical Society. All rights reserved.