Medium-range ordering in amorphous solids. Example: Amorphous polycarbonates

Abstract

Model calculations for special parallel ordering of chains in amorphous polycarbonate show development of a peak in the neutron scattering diagram in the medium-angle range, located at q = 1.25 A ̊ −1 ( q = 4π sinθ/λ) and its splitting for some deuterized samples. It is demonstrated that the development of this peak depends on the number of parallel chains and that at least three polycarbonate chains, each consisting of two monomer units (67 atoms), must be taken into consideration. These model calculations are in good accordance with the neutron scattering experiment and give at the same time a quantitative insight into the conceipt of clustering processes responsible for development of peaks in the X-ray or neutron scattering pattern in the region of q = 0.5 to 2 A ̊ −1 . Calculation of neutron scattering on the basis of quasiatoms which substituted characteristic configurations in the polycarbonate chain, enabled us to separate quantitatively the influence both of medium- and short-range ordering on the neutron scattering pattern.