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Nanocomposites are composites in which at least one of the phases shows dimensions in the nanometer range. These are high performance materials that exhibit unusual property combinations and unique design possibilities and are thought of as the materials of the 21st century. With an estimated annual growth rate of about 25% and huge demand for engineering polymers, their potential is so promising that they are useful in several applications ranging from packaging to bio-medical.
Polymer nanocomposites are materials in which nanoscopic inorganic particles, typically 10-100 A in at least one dimension, are dispersed in an organic polymer matrix in order to dramatically improve the performance properties of the polymer. Systems in which the inorganic particles are the individual layers of a lamellar compound - most typically smectite clay or nanocomposites of a polymer (such as nylon) embedded among layers of silicates - exhibit dramatically altered physical properties relative to the pristine polymer. For instance, the layer orientation, polymer-silicate nanocomposites exhibit stiffness, strength and dimensional stability in two dimensions (rather than one). Due to nanometer length scale which minimizes scattering of light, nanocomposites is usually transparent.
Polymer nanocomposites represent a new alternative to conventionally filled polymers. Because of their nanometer sizes, filler dispersion nanocomposites exhibit markedly improved properties when compared to the pure polymers or their traditional composites. These include increased modulus and strength, outstanding barrier properties, improved solvent and heat resistance and decreased flammability.
Polymers that contain transition metal complexes either attached to or directly in a n-conjugated backbone are an exciting and a promising class of modern materials. These macromolecules are hybrid of n-conjugated organic and transition metal containing polymers. N-conjugated organic polymers, such as polyacetylene, poly thiophene, and polypyrrole, as well as oligomers and derivatives of these materials have been extensively explored. These materials are endowed with many important properties such as nonlinear optical properties, electronic conductivity and luminescence, and have been proposed for their use in various applications including chemical sensors, electroluminescent devices, electro catalysis, batteries, smart windows and memory devices.
In recent years considerable efforts have been devoted to the development of methods for the preparation of composite particles consisting of polymer cores covered with shells of different chemical composition. In several of these powders, particles covered with magnetic materials have been used as beads for gas separation, or as pigments, catalysts, coatings, flocculents, toners, raw materials recovery, drug delivery and anticorrosion protection.
Polymer composites containing ferrites are increasingly replacing conventional ceramic magnetic materials because of their mould ability and reduction in cost. They are also potential materials for microwave absorbers, sensors and other aerospace applications. These flexible magnets or rubber ferrite composites are possible by the incorporation of magnetic powders in various elastomer matrices. This modifies the physical properties of the polymer matrix considerably.