Layered structures of shear-oriented and multilayered PEO/silicate nanocomposite films

Abstract

The structure and orientation of polymer and clay platelets in multilayered, micrometer-thick nanocomposite films was investigated by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), optical microscopy and small-angle neutron scattering (SANS). Microscopic and scattering methods complementarily measured the morphology and shear-induced orientation of polymer and platelets in films when spread layer by layer from a network-like polymer clay solution. During the drying process, the polymer clay network collapsed and clay platelets oriented inside the network with the clay surface normal perpendicular to the spread direction (x–z plane). On nanometer length scales, SANS and AFM yielded structure and orientation of platelets and polymer in and perpendicular to the spread direction of the film. SEM investigations led to the observation of unexpected morphology on the micron length scale. SEM did not detect boundaries between single spread, micron-thick film layers but, surprisingly, showed a highly ordered and layered structure of the film. Polarized light microscopy showed differences in birefringence in each plane.