Fabio Garbassi

N,N-Dialkylcarbamato complexes as precursors for the chemical implantation of metal cations on a silica support. Part I. Tin

Abstract Chemical implantation of tin on a commercial silica has been carried out by using the hydrocarbon soluble Sn(O 2 CN i Pr 2 ) 4 as precursor, the N,N -dialkylcarbamato group is chemically displaced by the silanol groups of the support under mild conditions.

N,N-Dialkylcarbamato complexes as precursors for the chemical implantation of metal cations on a silica support

Implantation of platinum(ii) on a commercial silica has been carried out under mild conditions by usingN,N-dialkylcarbamato complexes as reactive precursors, in a biphasic liquid/solid system, carbon dioxide and secondary amine being released during the reaction with the acidic silanol groups of the support. Information about the coordination sphere of the silica-supported platinum(ii) has been obtained by IR, XPS, solid-state NMR spectroscopy and WAXS measurements, which agree with chemical evidence. Reduction, either thermal or with dihydrogen, produces platinum nanoparticles, which were studied by conventional techniques and shown to be catalytically active in the hydrogenation of cyclohexene.

N,N-Dialkylcarbamato complexes as precursors for the chemical implantation of metal cations on a silica support. Part 3 Palladium

Chemical implantation of palladium(II) has been carried out under mild conditions by reacting trans-Pd(O 2 CNEt 2 ) 2 (NHEt 2 ) 2 with the silanol groups of amorphous silica, carbon dioxide and secondary amine being released in the process. The palladium-containing silica has been characterized and the coordination environment of the implanted cation has been defined by 13 C CP MAS NMR, DRIFT and XPS spectra, and by WAXS measurements. Silica-bonded palladium(II) was reduced thermally in vacuo or with dihydrogen at room temperature. Catalytic activity in the hydrogenation of cyclohexene was found for all samples containing the silica-supported reduced palladium; the best results, with rates independent of olefin concentration, were found for the samples treated thermally (200°C) under reduced pressure.

Loading silica with metals (palladium or platinum) under mild conditions by using well-defined molecular precursors

The loading of pre-treated amorphous silica with platinum or palladium was carried out by using the molecular precursors Pt2(micro-Cl)2Cl2(CO)2, or Pd2(micro-Cl)2Cl2(CO)2, respectively, which contain the required amount of coordinated CO to carry out the formation of the metal particles upon contact with moisture. The reactivity of the well-soluble mononuclear platinum complex cis-PtCl2(CO)2 with stoichiometric amounts of water was investigated either under N2 or CO. The metal nanoparticles produced on the silica matrix have been characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalytic performance of the silica-supported metals thus produced was evaluated in the hydrogenation of cyclohexene.

The morphology of rubber-modified acrylic adhesives

Abstract Toughened methacrylate-based pastes form a family of structural adhesives with some outstanding properties. During polymerization some phase separation occurs between the elastomeric toughener and the matrix. An investigation of the influence of the elastomer characteristics and of the curing temperature on the morphology of the hardened material was carried out using transmission electron microscopy and dynamical-mechanical spectroscopy.

Fractionation of linear saturated (co)polyesters by differential precipitation

SummarySamples of poly(ethylene terephthalate) (PET), poly(ethylene terephthalate-co-naphthalene-2,6-dicarboxylate) (PENT) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN), materials which find application in textile and packaging industry, have been investigated, with the aim to obtain narrow molecular weight fractions suitable for further characterization. Preliminary results concerning with the fractionation of gram-quantities of the polyesters are reported, using a method based on the fractional precipitation from a phenol/1,2,4-thrichlorobenzene solution of the polymer, using n-heptane as non-solvent. Obtained fractions have been characterized by intrinsic viscosity measurements and Gel Permeation Chromatography analysis.

Study of water sorption effect on toughened acrylic adhesives

Abstract As part of a study on the plasticizing effect of absorbed moisture in polymeric materials, water sorption in acrylic adhesives toughened by different elastomers (chlorosulphonated polyethylene, butadiene-acrylonitrile rubber and a fluorinated rubber) was studied at three different temperatures. Transmission electron microscopy observations and dynamic-mechanical spectra showed that water sorption acts on both the morphology and the tan δ curves of the adhesives in a way which depended upon the nature of the toughened elastomer.

XPS and DSC Studies of Solution Cast Polystyrene/Poly(organophosphazene) Blends. I. Polystyrene/Poly(phenoxy)phosphazene

Blends of polystyrene (PS) with poly(phenoxy)phosphazene (PPN) were studied by differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). A third component, poly(2,6-dimethyl-1,4-phenylene ether) (PPE), was added with the aim of increasing compatibility of the blends. Tg values did not vary in the PS/PPN blends, indicating that the components are substantially incompatible. The addition of PPE did not change the situation much even though some compatibility between PPN and PPE was detected. XPS on the cast films showed that only PPN was present at the surface. The surface composition of the blends was found to be dependent on the preparation technique.

Platinum Nanoparticles on Silica Obtained Under Mild Conditions Using cis-PtCl2(CO)2 as Precursor

Physi-/chemisorption of cis-PtCl2(CO)2 on partially dehydroxylated amorphous silica followed by exposure to water vapor at room temperature or at 210°C produces platinum nanoparticles, through a reductive process involving both coordinated carbon monoxide and water. Incomplete removal of hydrogen-bonded water from the silica surface increases the implantation yield. XPS and TEM measurements are reported. The silica-supported platinum is catalytically active towards the hydrogenation of cyclohexene.

Molding of syndiotactic polystyrene under its melting temperature

Syndiotactic polystyrene (SPS), a thermoplastic polymer that exhibits a high T m in some crystalline forms, can be conveniently processed by a cold-compaction technique. Processing temperatures in the range of 150-210°C, well below the T m , v gives rise to physicomechanical properties comparable and even better than those obtained by thermal compression or injection molding. The optimum treatment temperature seems to fall around 175°C. X-ray diffraction analysis, thermal analysis, and density measurements suggest that such behavior is connected to phase transitions of SPS and favored by the presence of styrene included in the crystalline fraction.