Pyotr M. Valetsky

Interaction of metal compounds with double-hydrophilic block copolymers in aqueous medium and metal colloid formation.

Abstract The interaction of a ‘double-hydrophilic’ polyethyleneoxide-polyethyleneimine block copolymer (PEO-b-PEI) with AuCl3, PdCl2, Na2PdCl4, H2PtCl6·6H2O, Na2PtCl6·6H2O, and K2PtCl4 in aqueous medium was studied. Micellar structure formation was observed for all metal compounds except Na2PdCl4 where additional protonation of the polymer was required to induce micelle formation. The characteristics of the micelles formed depended strongly on the metal type, the molar ratio polymermetal compound, and the type of reducing agent. Micellization in the presence of AuCl3·H2O is accompanied with reduction of the salt and the formation of gold colloid without reducing agent induced by oxidation of the PEI block. The interaction with PtCl62− ions results in narrowly distributed micelles wi size depending on the metal compound loading. In the case of loading with H2PtCl6, it was found that the size and shape of the colloids can be controlled by changing the molar ratio PEI:metal salt. The lower is the metal loading, the smaller are the particles. In addition, differently shaped Pt colloids were observed. This phenomenon can be controlled by the relative ratio of reactants.

Synthesis of Pd-, Pt-, and Rh-containing polymers derived from polystyrene-polybutadiene block copolymers; micellization of diblock copolymers due to complexation

Novel Pt-containing polymers derived from Zeise salt and polystyrene-polybutadiene diblock (PS-PB) and triblock (SBS) copolymers have been synthesized. The comparison of complex formation peculiarities of Pd-, Rh-, and Pt-containing polymers derived from SBS with 72 wt.-% of PB and PS-PB with 15 wt.-% of PB displayed that a short PB block in PS-PB allows to maintain solubility of organometallic polymers even if intermolecular complexation is probable. Such a solubility was found to be provided by micellization in Pd-, Pt-, and Rh-containing polymers derived from PS-PB. Moreover, crosslinks formed due to complexation were shown to contribute to micellization: iron carbonyl complexes immobilized on PS-PB, where solely intramolecular complexes can be formed, do not provide micellization.

Functionalization of Magnetic Nanoparticles with Amphiphilic Block Copolymers: Self-Assembled Thermoresponsive Submicrometer Particles

For the first time the four block copolymers derived from 1-alkyl[2-(acryloyloxy)ethyl]dimethylammonium bromides with hexyl (ADA) or cetyl (ADHA) groups and 2-hydroxyethylacrylate (HEA) or N-isopropylacrylamide (NIPAM) were synthesized and employed for functionalization of monodisperse iron oxide nanoparticles (NPs). The polyADA (pADA) or polyADHA (pADHA) block consists of long hydrophobic tails (C(6) or C(16)) connected to a positively charged quaternary ammonium group, making this block amphiphilic. The second block was either fully hydrophilic (pHEA) or thermoresponsive (pNIPAM). The dependence of the NP coating on the length of the hydrophobic tail in the amphiphilic block, the composition of the hydrophilic block, and the NP sizes have been studied. Unusual self-assembling of iron oxide NPs into well-defined composite submicrometer particles was observed for pADHA-b-pNIPAM in the wide range of concentrations (at the pADHA repeating unit concentrations of 0.065 × 10(-2)-2.91 × 10(-2) mmol/mL per 1 mg/mL NPs) but only two concentrations, 1.62 × 10(-2) and 1.94 × 10(-2) mmol/mL, led to regular spherical particles. The thermoresponsive behavior of these composite particles was tested using ζ-potential and dynamic light scattering measurements, while the morphology of particles was characterized by transmission electron microscopy. Coating of NPs with pADHA-b-pHEA results in the formation of individually coated NPs. The different composite particle morphologies are explained by different properties of pHEA and pNIPAM. It is demonstrated that the composite particles based on pADHA-b-pNIPAM are responsive to a magnetic field and can be recommended as magnetic stoppers in biorelated membrane separations. The incorporation of Pd species in submicrometer particles makes them promising candidates for catalytic applications as magnetically recoverable catalysts with a high magnetic response.

Size distributions of metal nanoparticles in polyelectrolyte gels

Small-angle x-ray scattering is used to study size distributions of noble metal nanoparticles embedded in polyelectrolyte hydrogels with oppositely charged surfactants. A procedure is proposed to subtract matrix scattering and to extract pure scattering due to the nanoparticles allowing to evaluate their size distribution functions by means of a regularization technique. Two kinds of collapsed gel-surfactant complexes were studied: a complex of a cationic gel of poly(diallyldimethylammonium chloride) with an anionic surfactant sodium dodecyl sulfate (PDADMACl/SDS), and that of an anionic gel of poly(methacrylic acid) with a cationic surfactant cetylpyridinium chloride (PMA/CPC). Addition of a gold compound (HAuCl4⋅3H2O) to the PDADMACl/SDS system forms the metal compound clusters and leads to a partial distortion of the gel structure. After subsequent reduction of the gold compound with sodium borohydride (NaBH4) ordering in the gel disappears and gold nanoparticles are formed. Their size distribution inc...

Pd(II) nanoparticles in porous polystyrene: factors influencing the nanoparticle size and catalytic properties

In this paper for the first time we present a systematic study of the influence of hydrophobicity of Pd(II) compounds, (CH3CN)2PdCl2, (PhCN)2PdCl2, (Sty)(CH3CN)PdCl2, and (StyPdCl2)2, on nanoparticle (NP) formation in the pores of hydrophobic micro/mesoporous hypercrosslinked polystyrene (HPS). The morphology and composition of HPS–Pd nanocomposites were studied using transmission electron microscopy, X-ray fluorescence measurements, X-ray photoelectron spectroscopy, and liquid nitrogen physisorption. The size and location of Pd compound NPs were found to depend on hydrophobicity of the Pd(II) environment. Catalytic testing of these nanocomposites in D-glucose oxidation was carried out to illustrate the influence of nanoparticle size and environment on catalytic activity. The highest catalytic activity was achieved for (Sty)(CH3CN)PdCl2, forming smallest NPs and allowing an optimal hydrophobicity–hydrophilicity balance with HPS.

Metal colloid formation in the complexes of polyelectrolyte gels with oppositely charged surfactants

Abstract The interaction of Pt, Au and Ni ions with the complexes of cationic gel of polydiallyldimethylammonium chloride (PDADMACl) with two anionic surfactants: sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulphonate (SDBS) was investigated. After reduction of metal compounds by hydrazine-hydrate or sodium borohydride, colloidal particles of Pt, Au and Ni embedded in the body of the hydrogel were formed. It was found by small-angle X-ray scattering (SAXS) that when the PDADMACl/SDS complexes interact with metal ions, the nanostructures are disturbed and the degree of disordering depends on the type of metal compound. PDADMACl/SDBS complexes seem to be more stable towards metal ion incorporation. By SEM and AFM data it was shown that gold colloid formation is controlled by the ordering in the PDADMACl/SDS complex which prevents the aggregation of metal colloids.

Nanosized catalysts in fine organic synthesis as a basis for developing innovative technologies in the pharmaceutical industry

This investigation of the catalytic properties of noble metal nanoparticles stabilized in hypercrosslinked polystyrene (HPS) matrix shows the prospect for their application in regioselective oxidation region- and enantioselective hydrogenation, which represent key stages for the synthesis of the intermediates and final products of pharmaceutical industry. Commercial use of nanosized catalysts allows shortening the synthetic stages, increasing product yields, and improving the environmental safety of the existing industrial processes. In this review, the synthesis, structure and catalytic properties of mono- (Pt, Ru, Pd), bi- (Pt-Pd, Pt-Ru, Pd-Ru), and trimetallic (Pt-Pd-Ru) nanoparticles stabilized in the pores of a polymeric HPS matrix are discussed. Physicochemical investigations have shown that the formation of metal-containing nanoparticles depends on the properties of the porous polymeric structure, the nature of the initial metal precursor, and the synthesis conditions. The use of nanosized catalysts is revealed to be effective in the most important field of fine organic synthesis: preparation of materials for medicine, vitamins, and food additives (e.g., in the food and pharmaceutical industry).

Small-Angle X-ray Scattering Study of the Structure of Self-Organized Polymer Matrices and Formation of Imbedded Metal Nanoparticles

The structures of self-organizing polymer matrices based on collapsed gels and polyoctadecylsiloxanes have been studied by the methods of conventional and anomalous X-ray small-angle scattering with the use of the laboratory and synchrotron sources of X-ray radiation. The process of formation of metal nanoparticles in such matrices is also studied, their size distributions are calculated, and the models of localization of these particles in the polymer matrices are suggested. It is shown that growth of metal particles is controlled by the structure of the polymer network and is limited by the dimensions of its cells. The electron-density profiles of polycondensed octadecylsiloxane matrices are also calculated.

Platinum-containing polymeric catalysts in direct L-sorbose oxidation

Impregnation of hypercrosslinked polystyrene (HPS) with tetrahydrofuran (THF) or methanol solutions containing platinic acid resulted in the formation of Pt(II) complexes within the nanocavities of HPS. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water was obtained with the HPS-Pt-THF complex. The structure of the catalyst isolated after the induction period was analyzed by transmission electron microscopy and X-ray photoelectron spectroscopy. Electron micrographs revealed enlarged Pt nanoclusters, which were most likely responsible for the high catalytic activity and selectivity observed.

Nanosized Pt-, Ru-, and Pd-containing catalysts for organic synthesis and solution of environmental issues

Synthesis of Pt-, Ru-, and Pd-containing nanoparticles in the pores of polymeric matrix of hypercrosslinked polystyrene, their structure and catalytic properties are under consideration. Physicochemical studies have shown that metal nanoparticle formation depends on the properties of the polymeric matrix porous structure, the nature of metal precursors and the synthesis conditions. The study of catalytic properties of metal nanoparticles stabilized in mesoporous matrices showed promising applications of these systems in the reactions of selective oxidation and hydrogenation, which are intermediate stages in the synthesis of precursors of vitamins and medicines. In order to solve environmental problems, nanocatalysts were investigated in the processes of oxidative degradation of phenol and reductive denitrification of nitrates for purification of sewage and natural water.