Iridium(I)-Catalyzed Asymmetric Intermolecular Hydroarylation of Norbornene with Benzamide

Summary.  Starting from the dinuclear chloro-bridged Ir(I) complexes [IrCl(PP)]₂ (PP = (R)-(6,6′-dimethylbiphenyl-2,2′-diyl)-1,1′-bis-(diphenylphosphine), (R)-(6,6′-dimethoxy-biphenyl-2,2′-diyl)-1,1′-bis-(diphenylphosphine), and (R)-1-((S)-2-(diphenylphosphino-ferrocenyl))-ethyldicyclohexylphosphine), a new class of cyclopentadienyl Ir(I) complexes containing a chiral bisphosphine ([IrCp(PP)]) was prepared and characterized. These new complexes are suited precatalysts for the direct hydroarylation of norbornene with benzamide. 2-(exo-Norbornyl)-benzamide is formed with an enantiomeric excess of up to 94% by the use of 1 mol% iridium, albeit in low yield. Received July 10, 2000. Accepted August 27, 2000     

Microstructural Evolution of Titanium Carbonitride Based Materials During Oxidation

 Ti(C, N) based materials represent a new class of hard and wear resistant structural materials. Nowadays, the main field of applications is focused on metal cutting and finishing operations. For these kinds of applications usually the mentioned materials work in oxidizing environments at high temperatures. The thermophysical stability under these conditions represents therefore a key factor that influences the material’s performance, and consequently the tool life of the component in service. The present study aimed to investigate the oxidation behaviour of two different Ti(C, N)-WC based materials, the first containing 0.9 wt% of Co and the second 6.2 wt% of Ni and 2.9 wt% of Co. Cycled oxidation tests (20 hours each) were conducted with a muffle furnace in laboratory static air at 1000 °C up to 100 hours. During the initial transitory stage the competition between the mass gain due to the formation of solid TiO₂ (rutile) and the mass loss due to released volatile W oxides controlled the mass change; thereafter the oxidation process obeyed a linear law. Great microstructural modifications occurred on the (sub)surfaces of the oxidized samples: multiphase TiO₂ based scales grew upon the external surfaces of the oxidized specimens. Kinetics and oxidation mechanisms were proposed and discussed.     

Iridium(I)-Catalyzed Asymmetric Intermolecular Hydroarylation of Norbornene with Benzamide

 Starting from the dinuclear chloro-bridged Ir(I) complexes [IrCl(PP)]₂ (PP = (R)-(6,6′-dimethylbiphenyl-2,2′-diyl)-1,1′-bis-(diphenylphosphine), (R)-(6,6′-dimethoxy-biphenyl-2,2′-diyl)-1,1′-bis-(diphenylphosphine), and (R)-1-((S)-2-(diphenylphosphino-ferrocenyl))-ethyldicyclohexylphosphine), a new class of cyclopentadienyl Ir(I) complexes containing a chiral bisphosphine ([IrCp(PP)]) was prepared and characterized. These new complexes are suited precatalysts for the direct hydroarylation of norbornene with benzamide. 2-(exo-Norbornyl)-benzamide is formed with an enantiomeric excess of up to 94% by the use of 1 mol% iridium, albeit in low yield.     

Giant colloidal crystals of fluorine-containing polymer spheres in exhaustively deionized aqueous suspensions and in the presence of sodium chloride

 Gigantic colloidal single crystals (2–6 mm) are formed for fluorine-containing polymer spheres (120–210 nm in diameter) in exhaustively deionized aqueous suspensions. The spheres used are poly(tetrafluoroethylene) (PTFEA and PTFEB), copolymer of tetrafluoroethylene and perfluorovinylether (PFA) and copolymer of tetrafluoroethylene and perfluoropropylene (PTP). The phase diagrams of these spheres are obtained in the deionized suspensions and also in the presence of sodium chloride for PFA. The critical sphere concentrations of crystal melting (φ _c) for these spheres are around 0.0006 in volume fraction, which are close to, but slightly larger than, those of monodispersed polystyrene spheres (φ _c ≈ 0.00015) and colloidal silica spheres(φ _c = 0.0002–0.0004) reported previously. The crystals are largest when the sphere concentrations are a bit higher than the φ _c value and their size decreases as the sphere concentration increases. Reflection spectra are taken in sedimentation equilibrium as a function of the height from the bottom of the suspension. The static elastic modulus is estimated to be 10.8 and 28.7 Pa for PTFEA and PTP spheres at the sphere concentrations 0.00325 and 0.00322 in volume fraction, respectively. Received: 27 October 1999 Accepted in revised form: 16 November 1999     

EPMA and X-Ray Diffraction of the Degraded Fuel Bundle from the Phebus FPT1 Test

 The degraded fuel rod bundle from the second Phebus test (FPT1) was examined at ITU, Karlsruhe. Metallographic and microprobe analysis of the degraded fuel pieces were carried out. The fuel samples from the upper bundle and cavity edge were porous and had remnants of thick oxidised cladding adhering to them. Electron microprobe analysis line scans across the cladding-fuel interface showed interdiffusion of U and Zr, with U diffusing down the grain boundaries of the oxidised cladding, while point analyses revealed noticeable amounts of Zr (1.5–4.2 wt%) in the UO₂ fuel. EPMA oxygen measurements revealed in the upper part of the bundle a superstoichiometry of x = 0.3–0.4 in UO _2 + x , indicating that fuel fragments in this position had undergone considerable oxidation. X-ray diffraction of the corium pool disclosed a deformed cubic fluorite lattice of UO₂. The lattice parameter of a = 5.2984 ? was considerably reduced compared with pure, stoichiometric UO₂ and was consistent with a lattice containing approximately 45 mol% ZrO₂ that had undergone little oxidation. The corium’s nominal composition of (U_0.5Zr_0.5) O₂ also corresponded to its observed single phase microstructure.     

Morphology, crystallization behavior and properties of impact-modified polypropylene copolymer with or without sodium benzoate as a nucleating agent

 The morphology, crystallization behavior, and properties of an impact-modified polypropylene (PP) copolymer with or without sodium benzoate were investigated. The contents of ethylene–propylene rubber (EPR) in the reactor-made PP copolymer is about 15 wt%. For comparison, blends of PP and EPR containing the same EPR composition were prepared by melt-mixing. Morphological studies by scanning probe microscopy indicated that the impact-modified copolymer consists of three different phases, i.e., polyethylene, PP, and EPR phases, which is considerably different from the morphology of the conventional PP/EPR blend of the corresponding composition. The impact-modified PP copolymer exhibited a higher crystallization rate in terms of the lower crystallization half-time and thus higher thermal and mechanical properties, such as impact strength and hardness, than the PP/EPR blend did. The addition of sodium benzoate as a nucleating agent to the copolymer increased the crystallization rate and the mechanical properties. Received: 4 June 2001 Accepted: 31 October 2001     

The Potential Energies of Cohesion of a Crystalline Organic Enantiomer and the Racemate; on the Energy for the Liquid Racemate [1]

Summary. The cohesion potential energy of the crystal of one enantiomer of ethyl 3-cyano-3-(3,4-dimethyloxyphenyl)-2,2,4-trimethylpentanoate, −47.7 ± 0.1 kJ mol⁻¹ (0–90°C), was found out from the heat of sublimation (123.2 ± 5.1 kJ mol⁻¹, 78.6°C) and the kinetic energies for the gas phase and the crystal. It was found that the entropy function of Debye’s theory of solids mathematically agreed with the vibrational entropy of the gas (variationally obtained), allowing to disclose the vibrational energy using the Debye energy function (E _vib 835.0 kJ mol⁻¹ (78.6°C), E ⁰ included). E _kin for the crystal (771.1 kJ mol⁻¹ (78.6°C)) was obtained by Debye’s theory with the experimental heat capacity. The cohesion energy represented a moderate part of the sublimation energy. The cohesion energy of the racemic crystal, −44.2 kJ mol⁻¹, was obtained by the heat of formation of the crystal in the solid state (3.0 kJ mol⁻¹, 83.3°C) and E _kin for the crystal (by Debye’s theory). The decrease in cohesion on formation of the crystal accounted for the energy of formation. The change in potential energy on liquefaction of the racemate from the gas state was disclosed obtaining added-up E _{vib + rot} for the liquid in the way as to E _vib for the gas, the Debye entropy function being increasedly suited for the liquid (E _{vib + rot} 763.4 kJ mol⁻¹ (115.4°C)). Positive ΔE _pot, 13.0 kJ mol⁻¹, arised from the increase in electronic energy (Δ _l ν_mean − 154.3 cm⁻¹, by the dielectric nature of the liquid), added to the cohesion energy.     

Microanalysis of Hydrogen, Boron and Fluorine in Vesuvianite by Means of SIMS, EPMA and FTIR

Vesuvianite, a complex sorosilicate, often contains variable (from trace-to-minor-element) amounts of H, B and F. We describe a microanalytical study of H, B and F in vesuvianite by means of Electron Probe Microanalysis (EPMA), Secondary Ion Mass Spectrometry (SIMS), and single-crystal Fourier-Transform InfraRed (FTIR) spectroscopy. Most crystals investigated are B- (up to 3.67 wt% B₂O₃) and F-rich (up to 2.38 wt%); H₂O ranges from 0.243 to 0.665 wt%. The H data obtained by SIMS allowed us to calibrate the quantitative analysis of H₂O by FTIR spectroscopy. The resulting molar absorption coefficient (ɛ _i = 100 000 ± 2000 L · mol⁻¹ · cm⁻²) is in excellent agreement with working curves available from the literature. Moreover, the SIMS data allowed us to obtain the calibration curve to estimate the B₂O₃ content on the basis on the FTIR absorbance: a _i = 34000 ± 1400 · B₂O₃ (wt%).     

Potentiometric titration behavior of poly(acrylic acid) within a cross-linked polymer network having amide groups

This study aimed to investigate the effect of COOH group distribution within a polymer network having amide groups, with which the COOH could form hydrogen bonds. We employed here two polyelectrolyte gels composed of N-isopropylacrylamide (NIPA) networks, either copolymerized with acrylic acid (AA) or within which poly(acrylic acid) (PAA) was entrapped. Both gels (AA–NIPA ∼ 1:4 mol/mol) were prepared by aqueous red-ox polymerization with N,N’-methylenebisacrylamide as the cross-linker. Finely divided gels in NaCl solutions (0.025 and 0.1 M) were titrated with NaOH and back-titrated with HCl at 25 °C. The results of the copolymer gel (CG) agreed well with those of a linear copolymer and a nanoscale gel which had a similar AA content to CG. However, marked differences were observed in the titration behaviors of the AA-copolymerized and PAA-entrapped gels, mainly due to the hydrogen bonding between the entrapped PAA chain and its surrounding NIPA network.     

Influence of Second-Order Lines on the Quantitative Wavelength Dispersive Spectrometry Analysis at Low Accelerating Voltages

The study covers a problem frequently encountered in the quantification of the results of wavelength-dispersive spectrometry (WDS) for the composition analysis of thin films. The characteristics of a Parallel Beam Spectrometer and traditional WDS systems were examined and olivine mineral – (Mg, Fe)₂SiO₄ (O – 44.03 wt%, Mg – 31.1 wt%, Si – 19.56 wt%, Fe – 5.06 wt%, Ni – 0.16 wt%, Mn – 0.09 wt%) was used as a reference material. Low accelerating voltage at 7 kV and beam current 400 nA were applied. Both methods yielded 30–35% of Mn. This is attributed to the overlapping of the MnLα first-order and the MgKα second-order lines. Studies of the influences of the second- and the third-order lines show that the second-order lines from Kα and Lα X-ray counts affected significantly the obtained WDS spectra when the influence of Mα counts was insignificant. Furthermore, the third-order lines did not have a marked effect on the analysis results.     

Low-temperature Data for Carbon Dioxide

Summary. We investigated empirical data for the vapor pressure (154≤T≤196 K) and the heat capacity (12.52≤T≤189.78 K) of solid carbon dioxide. A computer algebra system (CAS) was used for all calculations. From the numerical point of view, we have adopted a cubic piecewise polynomial representation for the heat capacity and reached an excellent agreement between the available empirical data and the calculated ones. Furthermore, we have obtained values for the vapor pressure and heat of sublimation at temperatures below 195 right down to 0 K. The theoretical key prerequisites are: 1) Determination of the heat of sublimation of 26250 J · mol⁻¹ at vanishing temperature and 2) Elaboration of a ‘linearized’ vapor pressure equation that includes all the relevant properties of the gaseous and solid phases. It is shown that: 1) The empirical vapor pressure equation derived by Giauque & Egan remains valid below the assumed lower limit of 154 K (a similar argument holds for Antoine’s equation), 2) The heat of sublimation reaches its maximum value of 27211 J · mol⁻¹ at 58.829 K and 3) The vapor behaves as a (polyatomic) ideal gas even for temperatures below 150 K.     

Structural, Spectroscopic, and Thermal Behaviour of Bis-(thiosaccharinate)-aqua-cadmium(II)

Summary.  The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. Received December 18, 2000. Accepted February 19, 2001     

Function and performance of silicone copolymer (VI). Synthesis and novel solution behavior of water-soluble polysiloxanes with different hydrophiles

Silicone surfactants containing different pendant hydrophilic groups such as diethanol tertiary amine (SHE, nonionic), diethanol methyl quaternary amine (cationic) and triethyl quaternary amine (cationic) have been synthesized and characterized by ¹H and ¹³C NMR and gel permeation chromatography. The solution behavior of these novel surfactants has also been investigated by surface tension measurement and a fluorescence method. It has been observed that the surface tension of these surfactants decreases as a function of time at a very low polymer concentration (1 × 10⁻⁴ wt%). At higher concentration (0.1 wt%), the equilibrium surface tensions reached very low values compared to that of typical polymer surfactants, for example, poly(ethylene oxide–propylene oxide) block copolymer (EPE0.8). In addition, the low I ₁/I ₃ values of these silicone surfactants indicate the formation of polymer aggregates in aqueous solution, and an extremely low I ₁/I ₃ value of SHE (1.06) compared to other polymeric surfactants (EPE0.8) and conventional surfactants [poly(ethylene glycol n-nonyl phenyl ethers), cetyltrimethylammonium bromide, and sodium dodecyl sulfate] indicates its stronger hydrophobicity. Received: 15 May 2000 Accepted: 18 October 2000     

Synthesis and flocculation performance of graft and random copolymer microgels of acrylamide and diallyldimethylammonium chloride

Graft (from linear homopolymers) and random (from a linear random copolymer) copolymer microgels of diallyldimethylammonium chloride (DADMAC) and acrylamide were synthesized via a free-radical mechanism using a γ-radiation technique. These copolymer microgels were evaluated as flocculants on a model dilute TiO₂ colloid suspension using a turbidimeter and a disc centrifuge photosedimentometer, and their performances were compared with the linear homopolymers and their blends. It was found that microgels produced after an appropriate irradiation time showed improved flocculation behavior over their nonirradiated linear counterparts. The graft microgels performed better than the corresponding random microgels. For a γ-radiation dosage of 100 krad/h, the graft microgels obtained by irradiating a 30% DADMAC (by weight) homopolymer blend for 3 h showed the maximum reduction in the relative turbidity of the TiO₂ suspension as well as the largest fraction of larger particles flocculated. Received: 18 May 1999 Accepted in revised form: 1 June 1999     

Synthesis and characterization of poly(styrene/α-t-butoxy-ω-vinylbenzyl-polyglycidol) microspheres

Polystyrene microspheres with polyglycidol (polyGL) in a surface layer were synthesized in batch radical emulsifier-free emulsion copolymerizations of styrene and surfmers, α-t-butoxy-ω-vinylbenzyl-polyGL macromonomers (VB-polyGL). Macromonomers with number-average molecular weight Mˉ _n=950 (VB-polyGL950) and Mˉ _n=2700 (VB-polyGL2700) were used for these polymerizations. In all syntheses the initial concentrations of styrene and initiator (K₂S₂O₈) were constant. The initial macromonomer-to-styrene ratios were varied from 1.10 × 10⁻³ to 1.64 × 10⁻² mol/mol and from 3.46 × 10⁻⁴ to 3.47 × 10⁻³ mol/mol for VB-polyGL950 and VB-polyGL2700, respectively. The diameters of microspheres obtained were smaller for the syntheses with higher concentrations of macromonomers. Syntheses with VB-polyGL950 yielded microspheres with number-average diameters (Dˉ _n) from 216 to 900 nm and with a bimodal diameter distribution. The number-average diameters of microspheres obtained with VB-polyGL2700 varied from 220 to 650 nm, depending on the initial concentration of macromonomer. Their diameter distributions were monomodal, with a diameter polydispersity parameter (ratio of weight-average and number-average diameters) in the range 1.007≤Dˉ _w/Dˉ _n≤1.022. For each type of microsphere the fraction of polyGL in a surface layer and the surface concentration of sulfate anions were determined. The fraction of polyGL in the surface layer was related to the initial monomer composition in the polymerizing mixture. Adsorption of human serum albumin onto surfaces of some poly(styrene/VB-polyGL) microspheres was up to 10 times lower than for the polystyrene microspheres obtained in a similar emulsifier-free emulsion polymerization of styrene. Received: 26 September 2000/Accepted: 19 February 2001     

High spin/low spin phase transitions of a spin-crossover complex in the emulsion polymerization of trifluoroethylmethacrylate (TFEMA) using PVA as a protective colloid

We have studied the magnetic properties of an Fe(II) spin-crossover complex near its high spin/low spin (HS/LS) phase transition in the emulsion polymerization of trifluoroethylmethacrylate (TFEMA) using poly(vinyl alcohol) (PVA) as a protective colloid, in comparison with sodium lauryl sulfate (SLS). Morphological analysis was used to establish that the nanodispersed spin-crossover complex was incorporated into the cores of polymer particles covered with PVA shells. The obvious bi-stability of the HS/LS phase transition was considered by the identification of multiplet states such as the triplet (S = 1) and quintet (S = 2) states, and the paramagnetic state (S = 1/2), by noting a gradual shift of g-value anisotropy in the electron spin resonance (ESR) spectrum at 5 K. This was thought to have arisen from the exchange interaction as a Jahn–Teller effect in the emulsion particles. Chemical modifications such as ligand substitution, and the nature of the central metal atom in the emulsion particle, especially influenced the HS/LS phase transition.     

Phase Transitions and Critical Behaviour of Binary Liquid Mixtures

Summary.  Compared to the simple one-component case, the phase behaviour of binary liquid mixtures shows an incredibly rich variety of phenomena. In this contribution we restrict ourselves to so-called binary symmetric mixtures, i.e. where like-particle interactions are equal (Φ₁₁(r) = Φ₂₂(r)), whereas the interactions between unlike fluid particles differ from those of likes ones (Φ₁₁(r) ≠ Φ₁₂(r)). Using both the simple mean spherical approximation and the more sophisticated self-consistent Ornstein-Zernike approximation, we have calculated the structural and thermodynamic properties of such a system and determine phase diagrams, paying particular attention to the critical behaviour (critical and tricritical points, critical end points). We then study the thermodynamic properties of the same binary mixture when it is in thermal equilibrium with a disordered porous matrix which we have realized by a frozen configuration of equally sized particles. We observe – in qualitative agreement with experiment – that already a minute matrix density is able to lead to drastic changes in the phase behaviour of the fluid. We systematically investigate the influence of the external system parameters (due to the matrix properties and the fluid–matrix interactions) and of the internal system parameters (due to the fluid properties) on the phase diagram. Received June 27, 2001. Accepted July 2, 2001     

Solvothermal Syntheses,Crystal Structures,and Properties of New [Mn(<Emphasis Type="BoldItalic">dien</Emphasis>)<Subscript>2</Subscript>]<Superscript>2+</Superscript> Complexes

Summary.  The two new compounds Mn(dien)₂[MoS₄] (1) and Mn(dien)₂[Mo₂O₂S₆] (2) (dien = diethylenetriamine) were prepared under solvothermal conditions. Both compounds were obtained as phase-pure products. The structures consist of new [Mn(dien)₂]²⁺ cations and isolated tetrahedral [MoS₄]²⁻ (1) or [Mo₂O₂S₆]²⁻ (2) anions. Between the anions and the cations, hydrogen bonding is observed. Compound 1 crystallizes in the tetragonal space group I (a = 10.219(2), c = 9.259(2) ?, Z = 2), whereas 2 crystallizes in the monoclinic space group P2₁/c (a = 8.703(2), b = 18.390(4), c = 14.603(3) ?, β = 103.18(3)°, Z = 4). The thermal behaviour of the thiomolybdates was investigated using difference thermoanalysis (DTA) and thermogravimetry (TG). Both compounds decompose under argon with a single endothermic signal in the DTA curve (peak maximum: 252 (1) and 242°C (2)). Received November 5, 2001. Accepted December 27, 2001     

pH-Responsive PEGylated nanogels as targetable and low invasive endosomolytic agents to induce the enhanced transfection efficiency of nonviral gene vectors

A pH-responsive PEGylated nanogel was successfully prepared by means of emulsion copolymerization of 2-(N,N-diethylamino)ethyl methacrylate (AMA) with heterobifunctional poly(ethylene glycol) (PEG) bearing a 4-vinylbenzyl group at the α-end and a lactose moiety at the ω-end in the presence of potassium persulfate and ethyleneglycol dimethacrylate as a cross-linker. Polyplex micelle composed of PEG-block-poly(l-lysine) copolymer and plasmid DNA (PEG-b-PLL/pDNA) exhibited a far more efficient transfection ability in the presence of lac-nanogel-8k-1.0% (PEG, M _n = 8000; cross-linking density, 1.0%) than the PEG-b-PLL/pDNA polyplex micelle alone (in the absence of lac-nanogel-8k-1.0%), suggesting that an appreciable fraction of lac-nanogel-8k-1.0% along with the PEG-b-PLL/pDNA polyplex micelle is taken up into the HuH-7 cells through the asialoglycoprotein receptor-mediated endocytosis process mediated by the cluster of a large number of lactose moieties on the surface of lac-nanogel-8k-1.0%, followed by the effective disruption of the endosome by the buffer effect of the unprotonated PAMA core in lac-nanogel-8k-1.0%. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Microemulsion polymerization of styrene using a polymerizable nonionic surfactant and a cationic surfactant

High polymer/surfactant weight ratios (up to about 15:1) of polystyrene microlatexes have been successfully produced by microemulsion polymerization using a small amount of polymerizable surfactant, ω-methoxypoly(ethylene oxide)₄₀ undecyl α-methacrylate macromonomer (PEO-R-MA-40), and cetyltrimethylammonium bromide (CTAB). After generating “seeding particles” in a ternary microemulsion containing only 0.2 wt% CTAB and 0.1 wt% styrene, the additional styrene containing less than 1 wt% PEO-R-MA-40 was added dropwise to the polymerized microemulsion for a period of about 4 h at room temperature. PEO-R-MA-40 copolymerized readily with styrene. The stable microlatexes were bluish-transparent at a lower polymer content and became bluish-opaque at a higher polymer content. Nearly monodisperse latex particles with diameters ranging from 50 to 80 nm and their molar masses ranging from 0.6 to 1.6 × 10⁶ g/mol could be obtained by varying the polymerization conditions. The dependence of the number of particles per milliliter of microlatex, the latex particle size and the copolymer molar mass on the polymerization time is discussed in conjunction with the effect of the macromonomer concentration. Received: 25 October/2000 Accepted: 2 February 2001