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Incoherent quasielastic neutron scattering results are reported for a number of polymer melts at temperatures well away from their glass transitions. The data are discussed in terms of the Rouse model, which is shown apparently to fit the scattering results over an unexpectedly wide range of frequency and momentum transfer. This effect is explained in terms of contributions to the observed scattering from interchain propagating modes.Differences between results are broadly explained by variation between polymers of their local backbone flexibility and by hindering effects of side groups. Values of monomeric friction coefficients are calculated from these results and give good agreement with those obtained from viscoelastic data.

The technique of neutron scattering from mixtures of protonated and deuterated molecules has been used to analyze the conformation of chains in poly(methyl methacrylate) (PMMA) plastically deformed in uniaxial tensile tests. Measurements were conducted on samples that had been stretched to extension ratios of a = 2.0-2.3 in a temperature range of T = 60-120 °C. The magnitude of the scattering vector covered a range of 0 < q < 6 nm"1. The results obtained in the low-q range demonstrate that on the scale of the radius of gyration the deformation is approximately affine in the macroscopic strain tensor for long chains (M" = 170000 and 250000) but markedly nonaffine for very short ones (Mw = 6000). In the intermediateand high-q range the scattering curve of unstretched PMMA is compared with the scattering curve of stretched PMMA measured perpendicular to the draw axis. The results suggest that pronounced nonaffine modes of plastic deformation are active in regions of less than 2.5 nm.