Neutron Scattering from Solid Polymers

TL;DR: Neutron scattering (NS) has become the central technique for investigating polymer conformations in the solid state on a scale larger than the typical monomer-monomer distance as mentioned in this paper, since it is the long chain nature of polymers which gives them their distinctive properties (e.g. rubber elasticity, non-Newtonian flow, viscoelasticity) NS is now essential in relating these properties to molecular structure.

Abstract: Neutron scattering (NS) has become the central technique for investigating polymer conformations in the solid state on a scale larger than the typical monomer-monomer distance. Since it is the long chain nature of polymers which gives them their distinctive properties (e.g. rubber elasticity, non-Newtonian flow, viscoelasticity) NS is now essential in relating these properties to molecular structure. The key property for molecules which are labelled is the scattering contrast between 1H and 2H isotopes. From a historical point of view, the emphasis early in the development of polymer science on solutions was partly because light scattering could be used to determine coil sizes. The scattering contrast is then between the different refractive indices of polymer and solvent. The fundamental results concerning Gaussian coils for the (amorphous) solid were only inferred by analogy with solutions, and these inferences were only verified much later by NS. In the case of crystalline polymers the situation was even less certain since there was no ‘model system’ analogous to solutions. Electron microscopy could in this case place limits on the types of conformations (they had to include chain folding) but could not, for example, determine the overall size of the molecules. Although the interest in NS has often centred on this ability to measure scattering functions for individual molecules, other uses are also important, e.g. concerning density distributions (as in small angle X-ray scattering) and spectroscopic information.