Abstract
Previous studies on polymer/clay nanocomposites indicate that the mechanical properties of the nanocomposites are highly sensitive to the dispersion of clay particles in the polymer matrix. Therefore, the characterization of the exfoliated clay structure in polymer matrices is essential to understand the structure-property relationships to get the desirable properties of the polymer/clay nanocomposites. In order to develop and characterize exfoliated polymer/clay nanocomposites, we have studied a series of polyisoprene (PI)/clay nanocomposites as a function of the clay weight fraction (w = 0-0.09) at 50DGC. We use X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), rheometry, and plasma-induced coating to study the structure and viscoelastic properties of aggregated, intercalated, and exfoliated PI/clay nanocomposites. In general, the morphology and viscoelastic properties of polymer/clay composites is affected by such things as processing methods, the composition and dispersion of clays, as well as the compatibility between polymer and clays. The purpose of the present work is to develop an exfoliated polyisoprene (PI)/clay nanocomposite as a model system and to study the effects of exfoliation and clay volume fraction, *q, on the viscoelastic properties of the Pi/clay nanocomposites. We use four different montmorillonite (MMT) clays, natural unmodified clay, plasma-treated clays, and organically modified clay (OC), to examine the effects of the dispersions of clays and polymer-clay interactions on the viscoelastic properties of the PI/clay composites. We find exfoliation for the PI/OC nanocomposites, whereas conventional dispersion or intercalation is obtained for the other PI/clay composites. We also determine the effective maximum packing fraction of clay for the exfoliated PI/OC nanocomposites as the point of overlapping in the dynamic viscosity with increasing clay volume fraction.