Journal of Polymer Science Part B: Polymer Physics, Vol.40, No.15, 1590-1600, 2002
X-ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice
X-ray powder diffraction in reflection (Bragg-Brentano parafocusing geometry) is extensively used to characterize the structure of polymer/layered silicate nanocomposites (PLSNs). The large basal spacings (d(001)>2.0 nm) necessitates the collection of data at scattering angles (2theta) of less than 10degrees. The calculation of an ideal scattering profile for PLSNs provides an avenue to ascertain the influence of experimental parameters and the arrangement, organization, concentration, and composition of constituents on the experimentally observed pattern. This enables better experimental technique, more complete utilization of the scattering data, insight into inconsistencies between scattering and microscopy, and minimization of incorrect interpretation or overinterpretation of data. Because of the strong theta dependence of theoretical and experimental factors at low values of 2theta, careful sample preparation and data evaluation are necessary and should be complemented by microscopic observations, especially for PLSNs with low volume fractions of organically-modified layered silicates (OLS) that are suspected of having exfoliated morphologies. X-ray powder diffraction in reflection alone is insufficient to completely characterize and ascribe PLSN morphology.