PVP-kaolinite

Last typical examples, which may be taken in the literature, are surfactant-mediated intercalation with the incorporation of poly(p-phenylene) into M0O3 (26) (Fig. 6) or poly(ethylene glycoD-kaolinite (27) and PVP-kaolinite (28) by refined guest displacement methods. 

FIG. 14 XRD patterns of kaolinite samples (a) methanol-treated kaolinite sample with adsorbed PVP, (b) methanol-treated palladium/PVP/kaolinite nanocomposites. (The basal distances are denoted in the figure.)... 

Palladium and rhodium nanoparticles were prepared on kaolinite at different metal contents and at different metal/polymer monomer ratios. We studied polymer incorporation between the disaggregated kaolinite lamellae. When the aqueous PVP solution was contacted with kaolinite a broadened peak of Jl 3.6 mn was... 

Fig. 5 XRD patterns of rehydrated kaolinite, poly(A -vinyl-2-pyrrolidone) (PFP)/kaolinite, PVP/Pd/kaolinite, and Pd/kaoli-nite...

Fig. 6 TEM image and particle size distribution of medium molecular weight PVP-protected Pd kaolinite (1.0% Pd)...

Fig. 7 XRD patterns of the PVP-protected Rh kaolinite showing Rh nanoparticles intercalated in the interlamellar space at different polymer content...

In the present work, novel methods are also described for the generation of palladium nanoparticles on the layered silicate montmorillonite and kaolinite using various polymers. The nonionic poly(iV-vinyl-2-pyrrolidone) (PVP) and the cationic polyfdiallyldimethylammonium chloride) (PDDA) were used for the synthesis. 

FIG. 12 Schematic illustration of preparation of Pd nanoparticles stabilized by polymer/kaolinite composite, (a) Disaggregation of kaolinite, (b) adsorption of PVP, and (c) octylammonium ions on methanol-treated kaolinite. 

The TEM picture of the PdK sample shows spherical particles 2-4 mn in diameter attached to the kaolinite lamellae without any aggregation (Fig. 15a). Electron micrographs of the complexes containing nonionic PVP display relatively small, nearly monodisperse particles (Fig. 15h) that tend to link up as the polymer concentration is increased. Polymer concentration was foimd to have no effect on the Pd particle size (see Table 2). In samples containing cationic PDDA as the stabilizer, the size distribution of the particles formed was more polydisperse. Increasing the palladimn content not only increases the particle size but also enhances polydispersity. 

The synthesis of palladium nanoparticles on montmorillonite layer silicates was studied. The Pd particles were prepared in situ in the interlamellar space of montmorillonite dispersed in an aqueous medium. Macromolecules were adsorbed on the support from an aqueous solution, followed by adsorption and reduction of Pd ions. The Pd° nanoparticles appear and grow in the internal, interlamellar space as well as on the external surfaces of the lamellae. Well-crystallized kaolinite clay can be disaggregated by the intercalation of DMSO to individual lamellae, which may serve as excellent supports for metal nanoparticles. After the adsorption of palladium precursor, metal nanocrystals were reduced by hydrazine or sodium borohydride between the kaolinite lamellae, i.e., in the interfacial layer acting as a nanoreactor. The incorporation of nanoparticles between the lamellae was shown hy XRD measinements. This procedure makes possible the steric control and restriction of nanoparticle growth. The stability of nanoparticles can be further enhanced hy the addition of polymers (PVP) and surfactants (alkyl-ammonium salts) that are also adsorbed between the kaolinite lamellae. The presence of the particles was also verified and their sizes were quantified by TEM measurements. 

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