Ultrafine Metal Particles in Polymers and the Formation of Periodic Polymer Stripes

El‐Shall, M. Samy; Slack, W.

doi:10.1021/ma00128a074

Cited by 30 publications

(13 citation statements)

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“…Ultrafine metal particles or clusters were often used as catalysts for organic reactions. − However, there are few reports on the polymerization activated by ultrafine metal particles . Recently, El-Shall et al , reported a new polymerization method for isobutylene using metal ions produced by laser ablation. They ablated the metal target to produce metal ion, then metal ions reacted with isobutylene monomer vapor and generated ionized species.…”

Section: Discussionmentioning

confidence: 99%

Fabrication of Poly(diphenylsilylenemethylene) and Poly(diphenylsiloxane) Thin Films Using Fine Metal Particles

Rossignol¹,

Nakata²,

Nagai³

et al. 1999

Chem. Mater.

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A new polymerization technique based on the use of sputtered metal particles for the thermal ring-opening polymerization of 1,1,3,3-tetraphenyl-1,3-disilacyclobutane (TPDC) was developed. This method facilitates the synthesis of polydiphenylsilylenemethylene (PDPhSM) thin films which are difficult to make by conventional methods because of their insolubility and high melting point. TPDC was first evaporated on silicon substrates and then exposed to metal particle deposition by sputtering prior to heat treatment. The catalytic activities of Pt, Pt/Pd, Au, Cu, and Ag particles were examined. The chemical structure of the film was basically the same, whatever the kind of metal used. However, the polymerization efficiency and film crystallinity depended greatly on the kind of metal under the same sputtering and heating conditions. The parts of the initial TPDC films that were not subjected to metal sputtering were entirely evaporated from the films without any polymerization. This phenomenon allowed us to make small polymer patterns. This method was also applicable to the ring-opening polymerization of hexaphenylcyclotrisiloxane.

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Section: Discussionmentioning

confidence: 99%

Fabrication of Poly(diphenylsilylenemethylene) and Poly(diphenylsiloxane) Thin Films Using Fine Metal Particles

Rossignol¹,

Nakata²,

Nagai³

et al. 1999

Chem. Mater.

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“…Reaction 1 constitutes a specific initiation mechanism, in addition to catalysis, − ionizing radiation , electrode processes, − or impact by metal atoms or ions that were reported recently. − The initiation mechanisms can be best isolated and studied in the gas phase or in clusters, − and the results then applied to the condensed phase. For example, our recent studies of the reactions of metal ions with isobutene have lead to a novel technique for bulk polymerization by the impact of metal atoms and ions on the liquid monomer. , …”

Section: Introductionmentioning

confidence: 99%

Coupled Reactions of Condensation and Charge Transfer. 1. Formation of Olefin Dimer Ions in Reactions with Ionized Aromatics. Gas-Phase Studies

et al. 1997

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The toluene radical ion C6H5CH3 •+, generated by resonance two-photon ionization, does not react with a single isobutene molecule (i-C4H8) which has a significantly higher ionization potential (ΔIP = 0.42 eV). However, a reaction is observed involving two i-C4H8 molecules, to form the dimer ion C8H16 •+. A coupled reaction of dimer formation and charge transfer to the dimer is exothermic if the product is an ionized hexene with a low IP. Correspondingly, the observed nominal second-order rate coefficients, (5−25) × 10-12 cm3 s-1, are enhanced by a factor of >105 over the expected value for direct endothermic charge transfer. Pressure and concentration effects suggest a sequential mechanism that proceeds through a C6H5CH3 •+(i-C4H8) reactive π complex. The complex can isomerize to a nonreactive CH3C6H4-t-C4H9 •+ adduct, or react with a second i-C4H8 molecule to form a C6H5CH3 •+(i-C4H8)2 complex, in which the olefin molecules are activated by the aromatic ion. Similar reactions are observed in the benzene/propene system with a somewhat larger ΔIP of 0.48 eV, suggesting that the charge density on the olefin in the complex is still sufficient to activate it for nucleophilic attack. However, aromatic/olefin systems with ΔIP > 0.87 eV show no olefin dimer formation. At low [i-C4H8] and [Ar] number densities, the rate of formation of C8H16 •+ is proportional to [i-C4H8]2[Ar]. The corresponding fourth-order rate coefficient shows a strong negative temperature coefficient with k = 11 × 10-42 cm9 s-1 at 300 K and 2 × 10-42 cm9 s-1 at 346 K, suggesting that the mechanism can be efficient in low-temperature industrial and interstellar environments. The direct formation of the dimer bypasses the monomer olefin cation and its consequent side-reactions, and directs the products selectively into radical ion polymerization. The products and energy relationships that apply in the gas phase are observed also in clusters.

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“…27 Also available are cryochemical methods to cocondensate metals and solvent vapors at liquid nitrogen temperatures, yielding solventstabilized clusters. [28][29][30][31] Recently, supercritical solutions of metal complexes have also been used to incorporate clusters in poly-(4-methyl-1-pentene) and poly(tetrafluoroethylene). 32 A unique, simple approach using an electrochemical method results in stabilized, soluble nanoclusters from a wide variety of metals.…”

Section: Introductionmentioning

confidence: 99%

“…Other methods to form clusters in polymer films take advantage of the ability to bind cluster precursors to ionic polymers like Nafion , followed by reduction to metal clusters or use organometallics as precursors . Also available are cryochemical methods to cocondensate metals and solvent vapors at liquid nitrogen temperatures, yielding solvent-stabilized clusters. − Recently, supercritical solutions of metal complexes have also been used to incorporate clusters in poly(4-methyl-1-pentene) and poly(tetrafluoroethylene) …”

Section: Introductionmentioning

confidence: 99%

Structural Characterization of Catalytically Active Metal Nanoclusters in Poly(amide imide) Films with High Metal Loading

et al. 1997

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Noble metal clusters were generated and stabilized in poly(amide imide) (PAI) polymers in high dispersion and high concentration of typically 15 wt %. The loaded polymers were prepared as pore-free, mechanically stable membranes, which have been successfully tested for catalytic activity in membrane reactors. Pure Pd- and Ag-loaded as well as bimetallic Pd/Ag, Pd/Cu, Pd/Co, and Pd/Pb PAI films were investigated by means of X-ray absorption spectroscopy (XAFS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) to characterize the structure and morphology of the metal clusters in the protective polymer. The measurements consistently show a homogeneous distribution of metallic nanoclusters of 1−3 nm size with a smaller amount of larger aggregates up to 30 nm in some of the films. The precise cluster size and distribution critically depend on the solvents used (N-methyl-2-pyrrolidone, tetrahydrofuran) as well as on other preparation parameters such as the stirring time of the metal precursor/polymer solution. In the case of Pd/Ag and Pd/Pb bimetallic films no clear evidence for the formation of bimetallic clusters in the membrane, i.e. alloying of both metal components, is found. In Pd/Cu and Pd/Co membranes, chlorine from the CuCl2 and CoCl2 precursors reacts with Pd, which may influence the Pd catalytic behavior. Reduction of the oxidized metal nanoclusters by H2 at 300 K is quantitatively studied by means of XAFS and gas permeation. Optimum membrane preparation conditions are discussed with respect to the cluster formation mechanism.

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Ultrafine Metal Particles in Polymers and the Formation of Periodic Polymer Stripes

Cited by 30 publications

References 1 publication

Fabrication of Poly(diphenylsilylenemethylene) and Poly(diphenylsiloxane) Thin Films Using Fine Metal Particles

Fabrication of Poly(diphenylsilylenemethylene) and Poly(diphenylsiloxane) Thin Films Using Fine Metal Particles

Coupled Reactions of Condensation and Charge Transfer. 1. Formation of Olefin Dimer Ions in Reactions with Ionized Aromatics. Gas-Phase Studies

Structural Characterization of Catalytically Active Metal Nanoclusters in Poly(amide imide) Films with High Metal Loading

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