Polymer-Clay Nanocomposites and Polymer Brushes from Clay Surfaces
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This paper summarizes the recent advances in the synthesis of polymer–clay nanocomposite materials and polymer brushes on clay surfaces with the focus on the in situ polymerization method. This new type of composite materials is based on a wide range of polymers as the matrix and layered silicate clays as the reinforcing filler. Its advantages, structures, and synthesis routes as well as the special properties of layered silicate are briefly introduced. Among various synthesis methods including exfoliation–adsorption, melt intercalation, and in situ polymerization, detailed discussions are focused on the in situ polymerization approach, which is then categorized by the polymerization mechanism employed. A comprehensive coverage is given to the in situ free radical polymerization method, including free radical polymerization with original clay, organoclay modified with nonreactive ammonium cations or polymerizable surfactants, and clay intercalated with cationic initiator derivatives, i.e., the surface-initiated polymerization strategy. As different strategies applied by various studies are compared, the emphasis of the discussion is placed on the synthesis scheme and the resulting structure of the nanocomposites. Short discussions on polymer brushes and in situ living polymerization methods on clay particle surfaces are offered because of the limited number of related publications. From the standpoint of the category of polymeric materials, this review is primarily based on thermoplastic polymers that can be produced by polymerizing their vinyl monomers. Other materials from other in situ polymerization mechanisms, such as ring opening polymerization, are briefly introduced at the end of this paper.