Structural relaxation investigations of glassy polystyrene by radial distribution functions

Abstract

Abstract The structural relaxation of an atactic polystyrene under sub-T g annealing at 50°C and at 70°C was investigated by the radial distribution function (RDF) derived from its wide-angle x-ray scattering (WAXS). By recording the changes in RDF (i.e., ΔH(r), where r is the radial distance from an arbitrary reference atom) after it had been annealed for a certain period of days, and taking the integration of ΔAH(r) 2dr, we found that the atom density within structural domains in a size below 15 A was changed dramatically, but that the tendency leveled off as annealing proceeded. However, the atom density outside the domains is barely changed by sub-T g annealing. The size of the domain is similar to the statistical segment length reported in the literature. The behavior of the domains—that the segmental relaxation inside the domains in the initial sub-T g annealing is unconstrained by their neighbors outside the domains—is also similar to the behavior of the statistical segments. The domains are believ...