Synthesis of a layered crystalline AlSPP and reusable catalysts for epoxidation of unfunctionalized olefins

A type of organic–inorganic hybrid material layered crystalline AlSPP (AlSPP) was prepared under simple conditions, completely different to the traditional hydrothermal methods, by the reaction of oligo‐styrenyl phosphonic acid with aluminum acetate and sodium dihydrogen phosphate. The microstructure of AlSPP was characterized by X‐ray diffraction, FT‐IR, atomic absorption spectroscopy, N₂ volumetric adsorption, atomic force microscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. Based on the experimental date, the ideal structure model of AlSPP is proposed, which indicated that the layered crystalline AlSPP samples are special lamellar structure with many cavums, holes, channels and ravines on the surface, the interlamellar region and interlayer surfaces of the particles. Therefore AlSPP possesses excellent properties and has potential applications for heterogeneous asymmetric catalyst supports. Copyright © 2012 John Wiley & Sons, Ltd.     

The behavior of poly(amino acids) containing l‐cysteine and their block copolymers with poly(ethylene glycol) on gold surfaces

Poly(ethylene glycol) (PEG) is often used to biocompatibilize surfaces of implantable biomedical devices. Here, block copolymers consisting of PEG and l ‐cysteine‐containing poly(amino acid)s (PAA's) were synthesized as polymeric multianchor systems for the covalent attachment to gold surfaces or surfaces decorated with gold nanoparticles. Amino‐terminated PEG was used as macroinitiator in the ring‐opening polymerization, (ROP), of respective amino acid N‐carboxyanhydrides (NCA's) of l ‐cysteine (l ‐Cys), l ‐glutamate (l ‐Glu), and l ‐lysine (l ‐Lys). The resulting block copolymers formed either diblock copolymers, PEG‐b‐p(l ‐Glu_x‐co‐l ‐Cys_y) or triblock copolymers, PEG‐b‐p(l ‐Glu)_x‐b‐p(l ‐Cys)_y. The monomer feed ratio matches the actual copolymer composition, which, together with high yields and a low polydispersity, indicates that the NCA ROP follows a living mechanism. The l ‐Cys repeat units act as anchors to the gold surface or the gold nanoparticles and the l ‐Glu repeat units act as spacers for the reactive l ‐Cys units. Surface analysis by atomic force microscopy revealed that all block copolymers formed homogenous and pin‐hole free surface coatings and the phase separation of mutually immiscible PEG and PAA blocks was observed. A different concept for the biocompatibilization of surfaces was followed when thiol‐terminated p(l ‐Lys) homopolymer was first grafted to the surface and then covalently decorated with HOOC‐CH₂‐PEG‐b‐p(Bz‐l ‐Glu) polymeric micelles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 248–257     

Novel Supports for Ethylene Polymerisation Based on Polystyrene Polymers

The industrial use of metallocene/methylaluminoxane catalytic systems and late transition metal catalysts requires the use of supports to directly get polyethylene (PE) with spherical morphology. The presence of residues of the inorganic support gives rise to PE contamination problems, therefore less contaminating organic supports may present an interesting alternative. In this work, linear hydroxypolystyrene (PS-OH) and polystyrene-block-isoprene copolymer (PS-b-PI) were tested as supports for ethylene polymerisation. The ability of these polymers when dissolved in a selective solvent to form micelles or aggregates, was investigated by light scattering techniques. Next, their capacity to act as MAO or TMA-activated supports towards MeDIP(2,6-iPrPh₂FeCl₂) catalyst was analysed by carrying ethylene polymerisation tests and PE morphology studies. The PS-b-PI copolymer, used as organic support in heptane, enabled the obtention of PE with well defined spherical morphology.     

Synthesis of polymer microspheres functionalized with chiral ligand by precipitation polymerization and their application to asymmetric transfer hydrogenation

Monodisperse, crosslinked poly(divinylbenzene) and poly(methacrylic acid‐co‐ethylene glycol dimethacrylate) microspheres with (1R,2R)‐N¹‐toluenesulfonyl‐1,2‐diphenylethylene‐1,2‐diamine ((R,R)‐TsDPEN) moiety were successfully prepared by precipitation polymerization. Introduction site of the (R,R)‐TsDPEN moiety into the polymer microspheres could be controlled by changing the order of addition of the corresponding monomers. The functionalized polymer microspheres were applied to asymmetric transfer hydrogenation of ketone and imine. Polymer microsphere‐supported chiral catalysts showed good reactivity and enantioselectivity in the catalytic asymmetric transfer hydrogenations. Chiral secondary alcohol was quantitatively obtained with 94% ee in the asymmetric transfer hydrogenation of acetophenone in water. We also found that introduction site of the chiral catalyst and hydrophobicity of the microspheres, as well as degree of the crosslinking, affected the yield and enantioselectivity of chiral product in this reaction. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3340–3349, 2010     

Optimal ATRP‐Made Soluble Polymer Supports for Phosphoramidite Chemistry

Soluble polystyrene supports with optimal molecular structures for iterative phosphoramidite chemistry were prepared by atom‐transfer radical polymerization (ATRP) and subsequent chain‐end modification steps. The controlled radical polymerization of styrene was first performed in the presence of an 9‐fluorenylmethoxycarbonyl (Fmoc)‐protected amino‐functional ATRP initiator. Soluble supports of different molecular weight were prepared. Size‐exclusion chromatography and NMR analysis indicated formation of well‐defined polymers with controlled chain lengths and narrow dispersity. After synthesis, the bromo ω end group of the ATRP polymer was removed by dehalogenation in the presence of tributyltin hydride, and the Fmoc protecting group of the α moiety was subsequently cleaved with piperidine. The resulting α‐primary amine was afterwards treated with a linker containing a carboxyl group, a cleavable ester site, and a dimethoxytrityl‐protected hydroxyl group to afford ideal soluble supports for phosphoramidite chemistry. NMR analysis indicated that these chain‐end modifications were quantitative. The supports were tested for the synthesis of a non‐natural sequence‐defined oligophosphates. High‐resolution ESI‐MS analysis of the cleaved oligomers indicated formation of uniform species, and thus confirmed the efficiency of the ATRP‐made soluble polymer supports. In addition, the synthesis of a thymidine‐loaded soluble support was achieved.     

Synthesis, characterization and evaluation of sulfonic resins as catalysts

Ion-exchange resins have been often used as catalysts especially those based on styrene-divinylbenzene copolymers with sulfonic acid groups in the aromatic rings of polymer chains. That is due to the advantages of heterogenous catalysis over the homogeneous acid catalysis. Moreover, resin catalysts can often lead to high selectivity in organic reactions due to the matrix effects. Therefore, the study of copolymers synthesis conditions to determine the type of polymer structure produced as well as the characterization of sulfonic resins obtained thereof are of great interest. The current paper describes the synthesis, characterization and evaluation as catalysts of sulfonic resins derived from polymer supports synthesized by aqueous suspension polymerization of styrene and divinylbenzene. The reaction conditions were varied and polymer supports with different physical properties and morphological characteristics were obtained. The polymer supports were chemically modified by sulfonation. The resultant sulfonic resins had their catalyst activity evaluated in the esterification of acetic acid with n-butanol.     

Synthesis of amphiphilic particles in the presence of inert solvents and their application to lipase immobilization

To develop monodisperse amphiphilic polymer particles on which a large amount of lipase could be immobilized, we performed seed polymerizations of glycidyl methacrylate and allyl methacrylate in the presence of nonpolar inert and polar inert solvents. The amphiphilic porous polymer particles, which had both hydrophilic guanidino groups and hydrophobic stearoyl groups, were synthesized in the presence of n‐decane and had a large amount of macropores with diameters of 50–1000 nm. The amount of lipase immobilized on the amphiphilic particles synthesized in the presence of n‐decane was 3.85 times that of the lipase immobilized on the amphiphilic particles synthesized in the absence of a solvent. The immobilized lipase prepared with the amphiphilic particles synthesized in the presence of n‐decane exhibited a high transesterification activity in n‐hexane and could be used repeatedly without a considerable activity loss. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 874–884, 2002; DOI 10.1002/pola.10178     

Ethylene oxidation over Ag supported on novel carbon nano-structured supports

Summary The potential of graphite nanofiber (GNF) supported silver catalysts to function as a catalyst system for the partial oxidation of ethylene to ethylene oxide has been investigated at 220°C and atmospheric pressure. It was found that when the metal was dispersed on “platelet”GNF that had been modified by pretreatment in argon at 2300°C the performance of the catalyst was superior to that of the current commercial system Ag/a-alumina, when reacted under the same. It is suggested that the observed enhancement in both activity and selectivity is related to electronic perturbations in the metal particles when dispersed on a highly conductive support medium.</o:p>     

Effect of 1‐hexene comonomer on polyethylene particle growth and copolymer chemical composition distribution

An investigation of the polymer particle growth characteristics and polymer molecular weight and composition distributions in ethylene homopolymerization and ethylene/1‐hexene copolymerization has been carried out with a catalyst comprising a zirconocene and methylaluminoxane immobilized on a silica support. The presence of 1‐hexene leads to higher productivity and easier fragmentation of the support during particle growth. Crystallization analysis fractionation and gel permeation chromatography analysis of ethylene/1‐hexene copolymers prepared at different polymerization times reveals a broadening of the chemical composition distribution with increasing polymerization time as a result of the gradual formation of a relatively high‐molecular‐weight, ethylene‐rich fraction. The results are indicative of significant monomer diffusion effects in both homopolymerization and copolymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2883–2890, 2006     

Periodic Mesoporous Organosilicas: A Type of Hybrid Support for Water‐Mediated Reactions

Hybrid mesoporous periodic organosilicas (Ph‐PMOs) with phenylene moieties embedded inside the silica matrix were used as a heterogeneous catalyst for the Ullmann coupling reaction in water. XRD, N₂ sorption, TEM, and solid‐state NMR spectroscopy reveal that mesoporous Ph‐PMO supports and Pd/Ph‐PMO catalysts have highly ordered 2D hexagonal mesostructures and covalently bonded organic–inorganic (all Si atoms bonded with carbon) hybrid frameworks. In the Ullmann coupling reaction of iodobenzene in water, the yield of biphenyl was 94 %, 34 %, 74 % and for palladium‐supported Ph‐PMO, pure silica (MCM‐41), and phenyl‐group‐modified Ph‐MCM‐41 catalysts, respectively. The selectivity toward biphenyl reached 91 % for the coupling of boromobenzene on the Pd/Ph‐PMO catalyst. This value is much higher than that for Pd/Ph‐MCM‐41 (19 %) and Pd/MCM‐41 (0 %), although the conversion of bromobenzene for these two catalysts is similar to that for Pd/Ph‐PMO. The large difference in selectivity can be attributed to surface hydrophobicity, which was evaluated by the adsorption isotherms of water and toluene. Ph‐PMO has the most hydrophobic surface, and in turn selectively adsorbs the reactant haloaryls from aqueous solution. Water transfer inside the mesochannels is thus restricted, and the coupling reaction of bromobenzene is improved.