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Clay Delamination in Clay/Poly(Dicyclopentadiene) Nanocomposites Quantified by Small Angle Neutron Scattering and High-Resolution Transmission Electron Microscopy
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE
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Highly delaminated claypolydicyclopentadiene nanocomposites were prepared by in-situ, ring-opening metathesis polymerization of presonicated mixtures of the liquid dicyclopentadiene DCPD and organically modified Montmorillonite clays. Three nanocomposite series of increasing clay loadings and modified Montmorillonite PGW were synthesized. The dispersed microstructure of the clays in the nanocomposites was characterized by small-angle neutron scattering SANS, ultra-small-angle neutron scattering USANS, small-angle X-ray scattering SAXS, and high-resolution transmission electron microscopy HR-TEM. All clays were highly delaminated and well dispersed within their host matrixes. The mean number of individual clay platelets per tactoid was predicted by fitting SANS data to the stacked-disk model and measured directly from HR-TEM images of a large number of tactoids in each sample. SANS results were in good agreement with HR-TEM for composites with low clay concentrations however, deviations were observed at higher clay loadings. These deviations are discussed in terms of several factors not taken into account by the stacked-disk model a long-range interactions, which become more important at high loadings b departure of tactoid geometries from parallel stacks of rigid disks and c the polydispersity of tactoid thicknesses. SAXS peaks were not present for most of the synthesized nanocomposites, suggesting a high degree of clay delamination.
APPROVED FOR PUBLIC RELEASE