Relations between Line Widths of Proton Magnetic Resonance Spectra and Molecular Weight of Poly-γ-benzyl-L-glutamate

Abstract

MACROMOLECULES in solution tend to give broader nuclear magnetic resonance (NMR) spectral lines than small molecules because of the greater mobility of the latter. Thus the line width (W) of a proton resonance of a macromolecule would be expected to increase with an increase of its molecular weight, although this is not the case for random coil polymers such as polystyrene because of independent motion of the various segments of the polymer chain¹. There is some scattered experimental evidence to support the contention of an increase of line width with an increase of molecular weight for rigid macromolecules² and this probably accounts for some of the discrepancies in the literature on the question of whether or not a particular proton resonance can be observed in poly-γ-benzyl-L-glutamate (PBG) in solution (refs. 1, 3 and unpublished results of Bradbury and Fenn).