Polymer Nanocomposites in Emulsion and Suspension: an Overview¹

Polymer nanocomposites have been a subject of intense research in the recent yeas. By nanoscale dispersion of inorganic fillers in the polymer matrices, significant enhancements in the properties of the materials have been achieved at very low filler volume fractions. Different modes of nanocomposite synthesis have been developed in the recent years which include template synthesis, in-situ polymerization, melt intercalation and polymer or prepolymer adsorption from solution. The last methodology also covers emulsion and suspension polymerization techniques for the synthesis of nanocomposites. These emulsion and suspension modes of polymer nanocomposite synthesis have the advantage that the polymerization is carried out in the presence of water which does not allow buildup of viscosity and the heat dissipation from the system is also easily achieved. The potential thermal damage to the polymer and the organic modification usually encountered in the melt intercalation is also avoided in the case of emulsion and suspension polymerization. Different polymer systems have been reported like polystyrene, polyurethanes, epoxy, poly(methyl methacrylate), poly(N-isopropylacrylamide), poly(butyl acrylate) etc. Specific synthetic methodologies like surfactant free polymerization, controlled living polymerization etc. have also been reported to successfully achieve nanocomposites with superior properties than the pure polymers. Majority of the studies bring home the conclusion that the amount of clay as well as surface modification present on clay surface significantly affect the microstructure and properties of the nanocomposite particles. Apart from clay as filler, many studies also have used the spherical inorganic particles as reinforcements.