Polymer-layered silicate nanocomposites from model surfactants

A series of experiments has been designed and conducted to test a recent model for the morphological behavior of polymer-layered silicate (PLS) nanocomposites, where a PLS nanocomposite is composed of a homopolymer matrix, a layered silicate clay mineral filler, and an organic surfactant modifier. For nearly complete exchange of naturally occurring interlayer cations with model surfactants synthesized for this study, the effect of surfactant length on the morphology of polymer-layered silicate nanocomposites has been examined. Here, the surfactant and matrix homopolymer are both based on polystyrene (PS) and are, therefore, expected to be miscible. Small-angle X-ray scattering data show that no intercalation of the homopolymer into the modified layered silicate occurs. This finding is consistent with results for autophobic dewetting such as occurs with densely grafted polymer brushes, based on high surfactant coverages within the layered silicate galleries.