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The effects of finite polymer polydispersity on the pulsed field gradient nuclear magnetic resonance (PFGNMR) measurement of polymer self-diffusion coefficients is considered both theoretically and experimentally. It is found that polystyrene solutions characterized by a polydispersity Mw/Mn < 1.10 present little difficulty in the interpretation of PFGNMR data. Single-exponential echo decays are observed down to attenuations in excess of 0.05 and the ensemble self-diffusion coefficient obtained lies between Mn and Mw. Polymer blends have been studied and the use of deuterated polystyrene has enabled determination of the component self-diffusion coefficients. We observe considerable microscopic averaging of molecular diffusion rates, with the greatest perturbation being suffered by the higher molar mass components. An investigation of the relative importance of reptation and tube renewal as relaxation mechanisms for random coil polymers in semidilute solution reveals that tube renewal is a weak process.

Diffusion measurements have been made on a variety of molecular systems using deuterium NMR spin echoes in the presence of pulsed magnetic field gradients (deuterium PFGNMR). Consistency is found between self-diffusion coefficients (Ds) obtained separately by proton and deuterium observation in a common molecular species, d1-benzene, and the semiclassical Stejskal–Tanner relation is verified to high precision for j=1/2 and j=1. The influence of rf field inhomogeneity on PFGNMR is examined for j=1/2 and j=1 in theory and experiment and we show that an rf offset angle ΔΘ leads to a zero gradient intercept which depends on cos3 ΔΘ. We obtain the temperature dependence of Ds for D2O and also find the separate proton and deuteron Ds values over the entire mole-ratio range in D2O/H2O mixtures. It is shown theoretically that the presence of rank 2 tensor interactions in the nuclear spin Hamiltonian does not disturb the PFGNMR experiment performed using the solid-echo rf sequence except to introduce a zero gradient intercept. We report the first solid-echo PFGNMR experiment performed on deuterium in the presence of nonzero static quadrupolar interactions. Using the liquid crystal system K-palmitate/D2O we examine the diffusion anisotropy and orientational symmetry in both oriented single crystal and randomly oriented polycrystal samples. Finally we exploit deuterium labeling to obtain the diffusion coefficient of adrenalin in human blood plasma by deuterium PFGNMR.