Microstructural Evolution of Melt Intercalated Polymer−Organically Modified Layered Silicates Nanocomposites

Abstract

The microstructure of various (ordered and disordered) polymer−organically modified layered silicate hybrids, synthesized via static polymer melt intercalation, is examined with X-ray diffraction and transmission electron microscopy. The ordered intercalates exhibit microstructures very similar to the unintercalated organically modified layered silicate (OLS). Polymer intercalation occurs as a front which penetrates the primary OLS particle from the external edge. The disordered hybrids, on the other hand, exhibit heterogeneous microstructures with increased layer disorder and spacing toward the polymer−primary particle boundary. In these hybrids, individual silicate layers are observed near the edge, whereas small coherent layer packets separated by polymer-filled gaps are prevalent toward the interior of the primary particle. The heterogeneous microstructure indicates that the formation of these disordered hybrids occur by a more complex process than simple sequential separation of individual layers starting from the surface of the crystallites and primary particles. In general, the features of the local microstructure from TEM give useful detail to the overall picture that can be drawn from the XRD results and enhance the understanding of various thermodynamic and kinetic issues surrounding hybrid formation.