Metal-polymer nanocomposite

L. I. Trakhtenberg, G. N. Gerasimov, Metal-Containing Polymers Cryochemical Synthesis, Structure and Physicochemical Properties, in G. Carotenuto, L. Nicolais (Eds.), Metal/Polymer Nanocomposites, Wiley, New York, 2005, p. 37. 

S, Zavyalov, A, Timofeev, A. Pivkina, and J. Schoonman, Metal-polymer nanocomposites formation and properties near the percolation threshold in Nanostructured Materials Selected... 

Metal-Polymer Nanocomposites, Edited by Luigi Nicolais and Gianfranco Carotenuto ISBN 0-471-47131-3 Copyright 2005 lohn Wiley Sons, Inc. 

This perspective method of metal-polymer nanocomposites formation involves the synthesis of both a nanoparticle and its stabilizing polymer matrix in one place (essentially in one stage). Such an approach is conceptually unique, and the systems under consideration are chemically self-regulating ones and thus they have embodied the best solution of the given problem (i.e., the nanoparticles formation and stabilization in polymer systems). Although at present the method is realized on transition metal acrylates and maleinates... 

As can be seen from the discussion above, the polyelectrolyte gel-surfactant complexes present interesting hybrid metal-polymer nanocomposites, allowing a vast variety of incorporated metals and metal-polymer-surfactant structures. The limitations of these systems are their heterogeneous character (insoluble in any media) and excessive sensitivity to external parameters (pH, temperature, etc.). 

Similar to noble metal nanoparticles, Co nanoparticles can be prepared by incorporation of C0CI2 (which is almost insoluble in toluene) in the PS-( -P2VP micelles followed by reduction. This results in very small spherical particles (below Inm in diameter), the thermal treatment of which at 200°C for 2hr yields spherical nanoparticles with diameters in the range of 3-5 nm [38]. In the solid state these metal-polymer nanocomposites display extraordinarily high magnetization value at comparatively low Co content that is, we obtained a tenfold increase of the specific magnification density. 

Varying the polymer type and characteristics allows development of sophisticated metal-polymer nanocomposites with tunable properties and promise for future apphcations. Yet, one can expect vigorous development of this field for years to come so that new polymeric systems yielding better control over nanoparticle formation and properties will be designed. 

METAL-POLYMER NANOCOMPOSITE SYNTHESIS NOVEL fXS/TL/ AND IN SITU APPROACHES... 

Metal-polymer nanocomposites can be obtained by two different approaches, namely, in situ and ex situ techniques. In the in situ methods, metal particles are generated inside a polymer matrix by decomposition (e.g., thermolysis, photolysis, radiolysis, etc.) or chemical reduction of a metallic precursor dissolved into the polymer. In the ex situ approach, nanoparticles are first produced by soft-chemistry routes and then dispersed into polymeric matrices. Usually, the preparative scheme allows us to obtain metal nanoparticles whose surface has been passivated by a monolayer of -alkanethiol molecules (i.e., Crfiin+i-SH). Surface passivation has a fundamental role since it avoids aggregation and surface oxidation/contamination phenomena. In addition, passivated metal particles are hydrophobic and therefore can be easily mixed with polymers. The ex-situ techniques for the synthesis of metal/polymer nanocomposites are frequently preferred to the in situ methods because of the high optical quality that can be achieved in the final product. 

In this chapter, two new approaches for the synthesis of metal-polymer nanocomposite materials have been described. The first method allows the preparation of contact-free dispersions of passivated gold clusters in polystyrene, and it is based on a traditional technique for the colloidal gold synthesis—that is, the alcoholic reduction of tetrachloroauric acid in presence of poly(vinyl pyrrolidone) as polymeric stabilizer. The primary function of the stabilizer is to avoid cluster sintering, but it also allows us to isolate clusters by co-precipitation. It has been found that the obtained polymer-protected nanometric gold particles can be dissolved in alkane-thiol alcoholic solutions to yield thiol-derivatized gold clusters by thiol absorbtion on the metal surface. Differently from other approaches for thioaurite synthesis available in the literature, this method allows complete control over the passivated gold cluster structure since a number of thiol molecules can be equivalently used and the... 

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