Studies of Structure and Dynamics of Solid Polymers by Elastic and Inelastic Neutron Scattering

Abstract

Neutron scattering methods can be applied to solid polymers in order to investigate the structure of the bulk material as well as the nature of the molecular motion. A review of some recently performed studies is presented. Diffusional motion in crystals of chain molecules has been studied by means of quasielastic scattering for the case of n-C33H68 as an example for the relationship between structure and molecular motion. It can be shown that below the so-called rotational transition the paraffin crystals exhibit two types of molecular motion: a translational jump (Tt = 0.5 10-8 s) and a 180° -rotational jump (Tr =2.5 10-8s). The low frequency vibrations in n-alkanes as models of polyethylene have been investigated by means of inelastic incoherent scattering. The longitudinal acoustical mode as well as other lattice vibrations are observed with frequencies, which are in good agreement with the calculations by Kitagawa and Miyazawa. As examples for structure studies the results of neutron scattering of cellulose fibres “stained” by deuterium and of semi crystal 1ine statistical copolymers are mentioned. Further the problem of chain configuration in crystalline polymers is discussed to some extent. It is shown that the preliminary results obtained in various laboratories do not allow a uniform conclusion, but there is overwhelming evidence that in the case of crystal 1ization from the melt the observed scattering curves are inconsistent with the model of adjacent re-entry and regular folds. © IUPAC