Therban®HNBR系列专题讲座(四)Therban®HNBR与其他橡胶性能之对比(Ⅰ)

文中介绍了Therban HNBR的性能,并分别与其它橡胶的耐热、耐油性能、动态曲挠性能、低温性能等进行了详细的比较.     

Copolymerization of norbornene and methyl acrylate catalyzed by Nd(naph)<Subscript>3</Subscript>–Al(i-Bu)<Subscript>3</Subscript>

The copolymerization of norbornene (NB) and methyl acrylate (MA) catalyzed by Nd(naph)₃–Al(i-Bu)₃ and the structure of the copolymers are studied in this article. All polymerization reactions were carried out under nitrogen atmosphere using syringe technique. The copolymers are characterized by IR, ¹H NMR, ¹³C NMR, GPC, and TGA. Norbornene and methyl acrylate are 22.2 and 77.8 mol%, respectively, in the copolymer. The molecular weight distribution is M_w/M_n < 2.0. The molecular weight of copolymer changes with the change of NB/MA in molar ratio. Molecular weight and its distribution of copolymer decrease as molar ratio of NB/MA increases. The copolymerization can be performed in solvents such as aromatic hydrocarbon. The copolymerization can be obtained at room temperature, whereas the copolymer yield increases with increasing reaction temperature. The yield of copolymer changes with the Al/Nd molar ratio with a preferable Al/Nd molar ratio of 30.     

An Indium(III)‐Catalyzed Synthesis of 4,4‐Dichloro‐1‐aryl‐N‐alkyl‐1‐yn‐3‐amines via an Intermolecular C(sp2)?C(sp) Bond Formation

This paper demonstrates an indium(III) triflate‐catalyzed reaction of electron‐deficient α,α‐dichloroaldimines with terminal alkynes leading to a rapid and selective access to highly functionalized propargylic amines in good to excellent yields. The dichloromethylene moiety of the aldimine acts as an activating group to accomplish this transformation under very mild conditions.     

Structure of a catalytically active oxo-centered trinuclear cobalt complex triaqua-(μ<Subscript>3</Subscript>-oxo)-hexa(μ<Subscript>2</Subscript>-pivalato-O,O′)-tricobalt(III)

The structure of a catalytically active oxo-centered trinuclear cobalt complex, namely, [triaqua-(μ₃-oxo)-hexa(μ₂-pivalato-O,O′)-tricobalt(III)]¹⁺ · NO ₃ ^? · 3H₂O, has been determined using X-ray diffraction analysis. The compound crystallizes in the hexagonal crystal system, space group of symmetry P6₃/mmc, with the unit cell parameters a = 12.328(1) Å, c = 22.625(1) Å, V = 2978.1(4) ų, Z = 2, and ρ = 1.075 g/cm³. The final discrepancy factor is R1 = 0.0596 for 589 symmetrically nonequivalent reflections with I ? 2σ(I), wR2 = 0.1612, and GooF = 1.035. The high-symmetry complex [C₃₀H₆₀O₁₆Co₃]¹⁺ with symmetry D _6h and a diameter of ～11 Å is an oxo-centered trinuclear cluster consisting of three symmetrically equivalent Co(III) atoms. Among the oxo-centered trinuclear metal complexes known to date, this complex has the highest symmetry and differs by the presence of two chemically equivalent bridges between the metal atoms. Apart from the two positively charged symmetrically equivalent trinuclear complexes, the unit cell contains two symmetrically equivalent NO ₃ ^? ions (statistically disordered over four positions) and six crystal water molecules.     

Unprecedented cadmium(II) complex with (44 · 66) net topology and in situ ligand synthesis

Hydrothermal reactions of 4,4′-bipyridine-2,2′-dicarboxylic acid (H₂BPDCA) with Cu(II) and Cd(II) nitrate salts result in the formation of two complexes [Cu(2,4-Hpydca)₂(H₂O)₂] (1) and [Cd(2,4-pydca)]_n (2) with pyridine-2,4-dicarboxylate (2,4-pydca²⁻), rather than BPDCA²⁻, as ligand, namely the in situ transformation of H₂BPDCA to H₂pydca occurred under the hydrothermal conditions. Complex 1 has been previously reported from different synthetic route, however, complex 2 is the first binodal 5-connecting 3D framework with unprecedented (4⁴ · 6⁶) net topology. The results provide a new strategy for in situ ligand synthesis and construction of coordination polymers with specific topology.     

Fluxional Behavior of <Emphasis Type="Italic">cis</Emphasis>-Fe(DMeOPrPE)<Subscript>2</Subscript>(H)<Subscript>2</Subscript> (DMeOPrPE = 1,2-[bis(dimethoxypropyl)phosphino]ethane); Implications for the Pressure Swing Purification of Natural Gas

Materials such as trans-Fe(DMeOPrPE)₂(X)(H₂O)⁺ (DMeOPrPE?=?1,2-[bis(dimethoxypropyl)phosphino]ethane; X?=?Cl or H) show considerable promise as sorbents for the removal of N₂ from natural gas in a pressure swing process. One problem, however, is that in long-term tests these sorbents slowly degrade over a period of many weeks. This study probed the degradation mechanism for the purpose of finding ways to stabilize the sorbents. To investigate the likelihood of degradation initiated by Fe–P bond dissociation, the fluxional behavior of the related cis-Fe(DMeOPrPE)₂(H)₂ complex was investigated by variable temperature ¹P{¹H} NMR spectroscopy. Analysis of the spectra gave the following activation parameters for the fluxional process: ΔH^??=?11.6 kcal/mol and ΔS^??=??9.2 cal/mol K. These results suggest that Fe–P bond dissociation (20–45 kcal/mol) is not occurring in the fluxional process and by implication that Fe–P bond dissociation is not initiating the decomposition of the trans-Fe(DMeOPrPE)₂(X)(H₂O)⁺ sorbents. Consequently, macrocycle ligands may not be the best approach for stabilizing the sorbents, as we have previously proposed. A “tetrahedral jump” mechanism is proposed for the fluxional process in cis-Fe(DMeOPrPE)₂(H)₂.     

Synthesis and self-assembly of pH-responsive amphiphilic poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone)-<Emphasis Type="Italic">block</Emphasis>-poly(acrylic acid) copolymer

The pH-responsive amphiphilic poly(ε-caprolactone)-block-poly(acrylic acid) (PCL-b-PAA) copolymer was prepared by selective hydrolysis of one novel poly(ε-caprolactone)-block-poly(methoxymethyl acrylate) (PCL-b-PMOMA) block copolymer, which was synthesized by combining ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and atom transfer radical polymerization (ATRP) of methoxymethyl acrylate (MOMA). Selective hydrolysis of the hemiketal ester groups on the PMOMA block gave 100% deprotection without the cleavage of the PCL block. The self-assembly behavior of PCL-b-PAA was investigated by fluorescence spectroscopy, DLS and TEM. The spherical micelles were formed with the hydrophobic PCL block as the core and the hydrophilic PAA as the shell by a co-solvent evaporation method. Moreover, the size and size distribution of the micelles varied with pH value and ionic strength in aqueous solution. The cytotoxicity of the PCL-b-PAA was lower, which was confirmed by MTT assay.     

Synthesis and Magnetic Properties of Maghemite (γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>) Short-Nanotubes

We report a rational synthesis of maghemite (γ-Fe₂O₃) short-nanotubes (SNTs) by a convenient hydrothermal method and subsequent annealing process. The structure, shape, and magnetic properties of the SNTs were investigated. Room-temperature and low-temperature magnetic measurements show that the as-fabricated γ-Fe₂O₃ SNTs are ferromagnetic, and its coercivity is nonzero when the temperature above blocking temperature (T _B). The hysteresis loop was operated to show that the magnetic properties of γ-Fe₂O₃ SNTs are strongly influenced by the morphology of the crystal. The unique magnetic behaviors were interpreted by the competition of the demagnetization energy of quasi-one-dimensional nanostructures and the magnetocrystalline anisotropy energy of particles in SNTs.     

Kalrez®全氟弹性体系列专题讲座(二)——Kalrez®全氟密封件的设计

文中介绍了Kalrez(R)密封件的沟槽设计原则,安装Kalrez(R)全氟O形圈的方法,讨论了压缩永久变形在循环温度下对于密封效果的影响,研究了新型断面结构的密封件在燕尾槽中的使用效果.     

Solid Solution (AlN)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>(SiC)<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> ≈ 0.7) by SHS under High Pressure of Nitrogen Gas

Solid solution (AlN) _x (SiC)_1–x (x = 0.7) was prepared from Al–SiC mixtures by SHS under high pressure of nitrogen gas (50, 70 MPa) and characterized by XRD and SEM. Combustion product was found to have a wurtzite 2H structure with lattice parameters a = 3.10889 ± 0.00022 Å and c = 5.00741 ± 0.00080 Å.     

Polymerization of ethylene to branched poly(ethylene)s using <Emphasis Type="Italic">ansa</Emphasis>-η<Superscript>5</Superscript>-monofluorenyl cyclohexanolato zirconium(IV) complex/methylaluminoxane

ansa-η⁵-Monofluorenyl cyclohexanolato zirconium complex 3 was shown to be active for the polymerization of ethylene when activated with methylaluminoxane (MAO) at 5 bar. Up to a polymerization temperature of 40 °C, 3/MAO resulted in linear poly(ethylene)s with saturated chain ends. However, at polymerization temperatures of 60, 80, and 100 °C, a mixture of branched poly(ethylene)s, linear α-olefins and long chain alkanes was obtained. The poly(ethylene)s produced at 80 and 100 °C exhibited a bimodal molecular weight distribution indicative of multiple active species. Very high molecular weight (M _v > 5 × 10⁵) linear poly(ethylene)s were obtained using 3/MAO at 25 °C.     

Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine) as a polychelatogen to remove toxic metals using ultrafiltration and bactericide properties of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)–Cu<Superscript>2+</Superscript> complexes

Poly(l-lysine) is a water-soluble, synthetic polypeptide containing functional amine groups that help remove di- and trivalent metal ions from aqueous solutions. This polymer’s removal properties were studied under different experimental conditions: (1) competitive and non-competitive conditions; (2) different pHs; and (3) filtration factors. Under the conditions of the Liquid-Phase Polymer-Based Retention (LPR) technique, the cooper (II) ion interaction was found to be selective and efficient when compared to other divalent metal ions studied. However, interestingly, this selectivity disappeared when trivalent metal ions were present. The polymer–metal ion interactions are based on the amino groups of the side-chains as well as the polypeptide backbone chain. The removal of metal ions was strongly dependent on the pH. By structural characterization with FT-IR and EPR spectroscopy, participation of the amide and mainly amine groups was found to take place for the coordination. For the Cu²⁺, coordination through four amine nitrogen donor atoms in the primary coordination sphere was detected. Antibacterial activity tests were conducted with the poly(l-lysine)–Cu²⁺ complex and showed a higher activity in comparison with the precursors Cu²⁺ and poly(l-lysine) at the same concentrations for E. coli (6538P), a Gram-negative bacterium, and S. aureus (ATCC), a Gram-positive bacterium.     

Sonoelectrochemical (20 kHz) production of Co<Subscript>65</Subscript>Fe<Subscript>35</Subscript> alloy nanoparticles from Aotani solutions

This paper describes the production of alloy nanoparticles of Co:Fe ratio 65:35 from Aotani solutions in the presence of high power ultrasound (20 kHz). The production of this new type of alloy nanoparticles was performed potentiostatically and galvanostatically at (298 ± 1) K using a newly designed experimental set-up i.e. a ‘sonoelectrode’ producing short applied current pulses triggered and followed immediately by ultrasonic pulses. It was shown that cathode efficiencies decreased with increasing current densities and high nanoparticle yields were obtained at low current densities. Morphological and structural studies of the produced nanoparticles were performed by TEM, SEM, XRD, and SAED, and showed that the strongly aggregated Co₆₅Fe₃₅ alloy nanoparticles were predominantly formed, with prevalent body-centered cubic bcc crystalline structure; no redissolution of the nanoaggregates was observed and no separate Fe and Co metallic nanoparticles were produced sonoelectrochemically. The experimental value of the lattice parameter for bcc Co–Fe alloy was 2.85 Å and was in excellent agreement with literature values.     

Therban® HNBR系列专题讲座(九)性能优异的Therban®制汽车发动机支承

研究了氢化丁腈橡胶、氯丁橡胶、乙丙橡胶等合成橡胶代替天然橡胶,应用于汽车发动机支承的可能性.探讨了几种弹性体的动态性能及物理性能.研究结果表明,Therban(R)在动态性能与物理性能方面都比较优异,可满足新一代发动机支承弹性体的苛刻要求.     

Copolymerization of norbornene and <Emphasis Type="Italic">n</Emphasis>-butyl methacrylate catalyzed by bis-(β-ketoamino)nickel(II)/B(C<Subscript>6</Subscript>F<Subscript>5</Subscript>)<Subscript>3</Subscript> catalytic system

Abstract  

Copolymerization of norbornene with n-butyl methacrylate (n-BMA) was carried out with catalytic systems of bis-(β-ketoamino)nickel(II) complexes Ni{RC(O)CHC[N(naphthyl)]CH₃}₂ (R = CH₃, CF₃) and B(C₆F₅)₃ in toluene and exhibited high activity for both catalytic systems. Influence of the catalyst structure and comonomer feed content on the polymerization activity as well as on the incorporation rates were investigated. The catalysis was proposed to involve the insertion mechanism of norbornene and n-BMA catalyzed by bis-(β-ketoamino)nickel(II)/B(C₆F₅)₃ catalytic systems, and the decreasing polymerization activity with an increasing content of n-BMA in the feedstock composition could be attributed to the competition of carbonyl group coordination onto the Ni(II) active center instead of the olefin double bond. The reactivity ratios were determined to be r _n-BMA = 0.095 and r _norbornene = 12.626 by the Kelen–Tüd?s method. The copolymer films prepared show good transparency in the visible region.     

Therban® HNBR系列专题讲座(二)Therban® HNBR弹性体的硫黄与过氧化物交联

硫黄和过氧化物是橡胶常用的交联剂.对这两种硫化体系来讲,关键是如何缩短硫化时间并提高硫化胶的耐老化性能.文中叙述了用硫黄和过氧化物硫化的HNBR橡胶的性能.     

Polymorphism of 3,3′-dihydroxy-β,β-carotene-4,4′-dione (Astaxanthin)

Astaxanthin (AXT) 3,3′-dihydroxy-β,β-carotene-4,4′-dione, from the group of carotenoid, specifically as xanthophyll, is investigated in this work on its polymorphism. The method to obtain a second polymorph of AXT is described. Polymorph I can be purchased as a commercial product or obtained via phase transformation from polymorph II. Polymorph II can be prepared from polymorph I by a thermal treatment carried out in a differential scanning calorimetry (DSC). The resulting crystals are characterized by different analytical techniques. X-ray powder diffractometer (XRPD) and resonance Raman spectroscopy prove the existence of two different crystalline polymorphs. Simultaneous thermal analysis (STA) gives additional information on their thermal behaviors. Polymorph I melts at 230 °C and polymorph II melts at 216 °C. Phase transition experiment carried out by slurry conversion experiment reveals two polymorphs are monotropically related. Polymorph II is the metastable form.     

Spectral properties of glass (15Ga<Subscript>2</Subscript>S<Subscript>3</Subscript> · 85GeS<Subscript>2</Subscript>) doped with erbium

For chalcogenide glasses in the system (1 – x)[0.15Ga₂S₃ · 0.85GeS₂] · xEr₂S₃, the absorption and luminescence spectra are investigated and the X-ray diffraction analysis is performed. A small shift in the position of the erbium absorption band with the increase of its content in the glass indicates the decrease of the effective charge on it, while the negligible changes in the angle position of the first sharp diffraction peak points to the constancy of the glass’s intermediate-order parameter. The possibility of describing the dependence of the intensity of erbium luminescence on its concentration using the earlier suggested equation has been discussed.