Metal-polymer nanocomposite synthesis

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

Carotenuto, G., Nicolais, L., Martorana, B., Perlo, P. (2005) In Nicolais, L., Carotenuto, G. (eds.), Metal-Polymer Nanocomposites Metal-Polymer Nanocomposite Synthesis Novel ex situ and in situ Approaches, Chapter 5, Wiley Interscience, New York, p. 155. 

Carotenuto Gianfranco, Nicolais Luigi, Martorana Brunette, and Perlo Piero. Metal-polymer nanocomposite synthesis Novel ex situ and in situ approaches. In Metal polymer nanocomposites, Luigi Nicolais and Gianfranco Carotenuto (eds.), pp. 155-181. New-York John Wiley, 2005. 

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. 

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... 

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... 

Rao CNR, Kulkami GU, Thomas PJ, Agrawal W, Gautam UK, Ghosh M (2003b) Nanocrystals of metals, semiconductors and oxides novel synthesis and applications. Curr Sci 85 1041-1045 Rao CNR, Kulkami GU, Thomas PJ (2005) Physical and chemical properties of nano-sized metal particles. In Nicolais L, Carotenuto G (eds) Metal-polymer nanocomposites. WUey, Hoboken, New Jersey, pp 1-36... 

Ozkan, S. Zh., Dzidziguri, E. L., Krpacheva, G. R, Bondarenko, G. N. Metal-polymer nanocomposites based on polydiphenylamine and copper nanoparticles synthesis, structure and properties. Russian Nanotechnologies. 2011, Vol. 6. Na 11-12,78-83. Karpacheva, G., Ozkan, S. Polymer-metal hybrid structures based on polydiphenylamine and Co nanoparticles. Procedia Materials Science. 2013, V. 2,52-59. 

At the co-deposition of nanocomposite components formation of M/SC particles proceeds simultaneously with formation of a dielectric matrix, and the relationship between these processes determines the nanocomposite structure. This problem has been in detail investigated for the case of M/SC nanoparticles formation in polymer matrices. Synthesis of nanocomposite films by simultaneous PVD of polytetrafluoroethylene (PTFE) and Au has been carried out in works [62-64], Polymer and metal were sputtered under action of Ar ions and then the obtained vapors were deposited on substrates (quartz, glass, silica, mica, etc.) at various temperatures. Here, it is necessary to note that polymer sputtering cannot be considered as only physical process PFTE polymer chains destruct under action of high-energy ions, and formed chemically active low-molecular fragments are then deposited and polymerized on a substrate surface. 

The y-ray irradiation synthesis method, which can be carried out at ambient temperature and pressure in aqueous or non-aqueous solutions, has been developed to prepare nanomaterials of metals, alloys, elemental chalcogens, chalcoge-nide semiconductors and inorganic/polymer nanocomposites. 

It is reasonable that, in the synthesis of polymer nanocomposites, the y-ray irradiation method is convenient for growing nanofibers and nanowires of metal chalcogenides due to the shape-control of the macromolecules formed in situ. Figure 7.38 shows some of the resulting nanofiber-dispersed polymer composites,... 

In this coimection, a cryochemical solid-phase synthesis of metal-polymer systems is of special importance. As a result of such a synthesis, metal clusters and organometallic assemblies formed at low temperatures are buried in a polymer environment, which offers possibilities to stabilize and study these products over a large temperature range. This method was first offered and described in reference 10. The thermal rearrangement of the initial low-temperature system is governed by relaxation processes in polymer matrix. In particular, the aggregation of metal atom clusters to form metal nanocrystals in cryochemically produced metal-polymer systems yields new nanocomposite materials with valuable properties. The study of the mechanism of cluster aggregation, which depends on the characteristics of the polymer matrix, will allow the nanocomposite structure to proceed in the needed direction. Thus, it becomes possible to determine the methods of cryochemical synthesis of metal-polymer materials with predetermined properties. 

Figure 2.2. Schematic of apparatus for synthesis of a metal/SC-polymer nanocomposite 1, vacuum chamber 2, substrate holder 3, resistance measurements (for metal control in the film) 4, heater (metal evaporation) 5, heater (cyclophane evaporation) 6, heater (cyclophane pyrolysis).

JJi. Park, M. Atobe, and T. Fuchigami, Sonochemical synthesis of conducting polymer-metal nanoparticles nanocomposite, Electrochim. Acta, 51, 849-854 (2005). 

K.R. Reddy, K.P. Lee, Y. Lee, and A.I. Gopalan, Facile synthesis of conducting polymer-metal hybrid nanocomposite by in situ chemical oxidative polymerization with negatively charged metal nanoparticles. Mat. Letters, 62, 1815-1818 (2008). 

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