Chain conformation and structure in amorphous polymers as revealed by X-ray, neutron, light and electron diffraction

Publisher Website
Google Scholar
Abstract
The physical structure of the melt, the supercooled melt, and the glassy state of amorphous polymers can be characterized by the chain conformation, the local order, and the morphology. The conformation was studied by small-angle neutron scattering. The local order was characterized by pair distribution functions which were derived from electron scattering curves. In addition, model calculations were used to gain information about short-range order. The morphology was studied by means of light scattering (density and anisotropy fluctuations), small-angle X-ray scattering (density fluctuations), and magnetic birefringence measurements (orientational order). Experiments were performed on polyethylene melts and polystyrene, polymethyl methacrylate, and polycarbonate above and below the glass transition temperature. The results show that the amorphous phase is a homogeneous phase and that there are no anisotropic structures of the kind proposed by various bundle models of the amorphous phase. The chains assume a random coil conformation as suggested by Flory. The near-range order, which is determined by chain segments belonging to different interpenetrating chains, cannot be described by the assumption of a parallel packing of neighboring chains.