Controlling the miscibility of polyethylene/layered silicate nanocomposites by altering the polymer/surface interactions

Polyethylene/layered silicate nanocomposites are synthesized utilizing three types of polymeric surfactants/compatibilizers in order to influence the miscibility of polyethylene with the nanoparticle surface. The additives are designed so that they can play the role of a polymeric surfactant modifying the hydrophilic clay or of a compatibilizer with the organoclay. Model additives, especially synthesized for this study, included: polyethylene chains, which possess either a single functional end-group or multiple functional groups along the chain, as well as functional diblock copolymers. Maleic anhydrite grafted polyethylene with a low degree of functionalization was used as well. The structure of the resulting micro- or nanocomposites was investigated by X-ray diffraction and transmission electron microscopy. Immiscible hybrids as well as intercalated and/or exfoliated nanocomposites are obtained in a controlled way, depending on the kind of additive and its concentration in the mixture. The most important factor controlling the structure and the properties is the ratio of additive to nanoparticles. The rheological properties of the hybrids correlate well with the final micro- or nanostructure.