Reverse atom transfer radical polymerization of (-)-menthyl methacrylate

The reverse atom transfer radical polymerization(RATRP) of (-)-menthyl methacrylate ((-)-MnMA) with AIBN(AIBN/CuCl2/bipyridine(bipy) or (-)sparteine((-)Sp) =1/2/4) initiating system in THF has been studied. The dependence of the specific rotation on molecular weight was investigated.

Polymerization of acrylonitrile with (diisopropylamido) bis (indenyl) lanthanides

The polymerization of acrylonitrile was studied using ( diisopropylamido) his ( indenyl) lanthanides, Ind(2)LnN(i-Pr)(2)(Ln = Y, Yb) as a single-component catalyst. The effects of the amount of catalyst, monomer concentration and polymerization temperature on catalytic activity and molecular weight of polyacrylonitrile (PAN) were studied. The results show that the catalytic activity is raised obviously with rising polymerization temperature. The monomer conversion reaches 64% under polymerization temperature, monomer concentration and catalyst concentration are 50 degreesC, 5.1 mol . L (-1) and 0. 3 % (molar ratio) sequentially. The conversion and molecular weight of the polymer increase appreciably with adding additive, PhONa. When the molar ratio of PhONa to the catalyst is three I the conversion and the molecular weight is 76% and 1.32 x 10(4), respectively. The initiation mechanism for the polymerization of acrylonitrile was proposed.

Methanol tolerant FeTPP-Pt/C Co-catalysts for the electroreduction of oxygen

It was found for the first time that iron tetraphenylporphyrin (FeTPP)-Pt/C showed the good activity for the electroreduction of oxygen and methanol tolerant ability. Their performances were related to the heat-treatment temperature.

The preparation of phenolic resin/montmorillonite nanocomposites by suspension condensation polymerization and their morphology

Phenolic resin/clay nanocomposites were prepared using a suspension condensation polymerization method that was suitable to both novolac and resole. Natural montmorillonite and two kinds of organic modified montmorillonite were adopted to investigate the effect of modification on the final morphology of the nanocomposites. X-ray diffraction (XRD) measurements and Transmission Electron Microscope (TEM) observations showed that clay platelets were easier to be exfoliated or intercalated in novolac than in resole because novolac usually has a linear structure. The modifier with a phenyl ring was more compatible with novolac (or resole) than the aliphatic type modifier. The influence of curing on the morphology was studied as well. An exfoliation-adsorption and in situ condensation mechanism was proposed on the formation of the nanocomposites.

Effect of properties of active carbon supports on performance of Pt/C catalysts in polymer electrolyte membrane fuel cell

The Pt/C catalysts were prepared with pine active carbon and Vulcan XC-72 active carbon as the supports. The performances of the Pt/C catalysts in polymer electrolyte membrane fuel cell were compared. The result indicates that the performance of Pt/Vulcan XC-72 is better than that of Pt/pine. The physical and chemical properties of the two active carbons were measured using several analysis techniques. It was found that the pore size, specific conductivity and the surface function group significantly influence the performance of the electrocatalyst.

The influence of nucleating agent on crystallization behavior and properties of polypropylene and its copolymer with ethylene

The influences of nucleating agent EDBS on crystallization behavior and properties of polypropylene UP) and its copolymer with a small amount (4. 48 %, molar fraction) of ethylene (CPP) were studied. DSC results indicated that the crystallization temperature of iPP and CPP samples with 0.5 % (mass fraction) EDBS obviously increased and the degree of crystallinity of these samples became higher. In addition, adding small amount of EDBS enhanced the crystallization of the low isotacticity and low molecular weight segments of the CPP. PLM results showed that their spherulite size decreased markedly, and as a result, the transmittance and haze of the films were all improved.

Liquid-phase hydrogenation of furfural to tetrahydrofurfuryl alcohol catalyzed by polymer resin supported palladium catalysts

Three kinds of polymer resin supported Pd catalysts were prepared by mixing PdCl2, with alkaline styrene anion exchange resins[D392 -NH2, D382, -NHCH3, D301R, -NH(CH3)(2)], strongly alkaline styrene anion exchanged resin [201 X 7DVB, -NH+ (CH3)(3)] and alkaline epoxy exchange resin (701, -NH2), and hydrogenating in liquid phase at 1.013 X 10(5) Pa. The hydrogenation of furfural was studied under the reaction conditions such as solvent, temperature. Pd content in the supported catalyst and the amount of the catalyst. The yield of hydrogenation reaction of furfural markedly increased to 100% and the selectivity to tetrahydrofurfuryl alcohol increased to over 98% by polymer (alkaline styrene anion exchange resins D392, -NH2, D382, -NHCH3) supported palladium catalysts comparing with the yield over 70% and selectivity over 97% by palladium catalyst, in 50% alcohol-50% water or pure water solution at 1.013 X 10(5) Pa. The relationship between hydrogenation and the structures of functional group in the supporting resin was examined by XPS method.

Electrocatalytic performance of Pt-TiO2/C complex catalysts for oxidation of methanol

It is reported for the first time that the Pt-TiO2/C catalyst prepared with chemical reduction and sol-gel method showed the excellent electrocatalytic activity and stability for the electrooxidation of methanol. When the atom ratio of Ti to Pt in the catalysts is 1/2, the catalysts showed the best electrocatalytic properties. After the catalyst is treated at 500 degreesC, the performance is further improved. It is hopeful to use the catalyst in the pratical DMFC.

Synthesis and characterization of (C5H9C9H6)(2)Yb(THF)(2)(II) (1) and [(C5H9C5H4)(2)Yb(THF)](2)O-2 (2), and ring-opening polymerization of lactones with 1

Reaction of YbI2 with two equivalents of cyclopentylindenyl lithium (C5H9C9H6Li) affords ytterbium(II) substituted indenyl complex (C5H9C9H6)(2)Yb(THF)(2) (1) which shows high activity to ring-opening polymerization (ROP) of lactones. The reaction between YbI2 and cyclopentylcyclopentadienyl sodium (C5H9C5H4Na) gives complex [(C5H9C5H4)(2)Yb(THF)](2)O-2 (2) in the presence of a trace amount of O-2, the molecular structure of which comprises two (C5H9C5H4)(2)Yb(THF) bridged by an asymmetric O-2 unit. The O-2 unit and ytterbium atoms define a plane that contains a C-i symmetry center.

Preparation and characterization of poly(ethyl acrylate)/bentonite nanocomposites by in situ emulsion polymerization

Transparent poly(ethyl acrylate) (PEA)/bentonite nanocomposites containing intercalated-exfoliated combinatory structures of clay were synthesized by in situ emulsion polymerizations in aqueous dispersions containing bentonite. The samples for characterization were prepared through direct-forming films of the resulting emulsions without coagulation and separation. An examination with X-ray diffraction and transmission electron microscopy showed that intercalated and exfoliated structures of clay coexisted in the PEA/bentonite nanocomposites. The measurements of mechanical properties showed that PEA properties were greatly improved, with the tensile strength and modulus increasing from 0.65 and 0.24 to 11.16 and 88.41 MPa, respectively. Dynamic mechanical analysis revealed a very marked improvement of the storage modulus above the glass-transition temperature. In addition, because of the uniform dispersion of silicate layers in the PEA matrix, the barrier properties of the materials were dramatically improved. The permeability coefficient of water vapor decreased from 30.8 x 10(-6) to 8.3 x 10(-6) g cm/cm(2)s cmHg. (C) 2002 Wiley Periodicals, Inc.