Size Distribution and Anisotropy of the MinorPhase Droplets in Polypropylene/Ethylene-OcteneCopolymer Blends: Effects of Shear andComponent Miscibility简

In this work, polypropylene （PP）/octene-ethylene copolymer （POE） blends were injection-molded using the so- called dynamic packing injection technique, which imposed oscillatory shear on the gradually cooling melt during the packing solidification stage. In this way, the effect of shear on the size distribution and anisotropy of the minor phase droplets could be investigated. Besides, by using two kinds of POE with different octene contents, the effect of component miscibility was also studied. The results show that the droplet size is mainly determined by composition and miscibility, and droplet anisotropy is mainly determined by droplet size and shear. Most importantly, under the same processing condition, droplet anisotropy increases with droplet size, and there seems a linear fit between them, disregarding the miscibility factor. These results may provide guidance for preparing polymer blends with desired properties by tailoring their phase morphologies.     

Introduction of a Reliable Method for Determination ofIntrinsic Viscosity for Any Polymer with High Precision简

Intrinsic viscosities for a given polyelectrolyte in salt free and low-salt solvents reported in literatures are normally not comparable, because of inadequate valuation procedures. This article describes a theoretically justified reliable method, which is free of any model assumptions： The so called Wolf plot （logarithm of the relative viscosity as a function of polymer concentration） enables the unequivocal determination of intrinsic viscosities for all kinds of macromolecules, irrespective of whether they are chain molecules of different architecture or globular polymers, whether they are charged or uncharged. The validation of the method was examined by evaluation of the viscosities of a polyelectrolyte, some uncharged polymers of different architectures, uncharged polymer blends, and some literature data.     

In situ polymerization of aniline in electrospun microfbers简

Conductive microfibers with an average diameter of ca. 1.0 mm were prepared by in situ polymerization of aniline, in which poly(vinylchloride-acrylonitrile)(PVC-AN) was used as the filament-material in electrospinning to form precursor microfibers and carry the aniline monomers. Fourier-transform infrared(FTIR) results demonstrated that PANi was successfully polymerized in the microfibers. The morphology of the PVC-AN-PANi microfibers was observed by scanning electron microscopy(SEM). Results of differential scanning calorimetry indicated that the polymer composite of PVC-AN-PANi formed via molecular interactions. Although the conductivity of PVC-AN-PANi microfibers was still limited(2.2 fi 10à8S/cm), this method provided an effective and convenient approach for preparing highly uniform and soft microfibrous electrodes.     

Thermal Degradation,Flame Retardance and Mechanical Properties of Thermoplastic Polyurethane Composites Based on AluminumHypophosphite简

Aluminum hypophosphite （AP） was used to prepare flame-retarded thermoplastic polyurethane （FR-TPU） composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index （LOI）, vertical burning test （UL-94）, thermogravimetric analysis （TGA）, cone calorimeter （CC） test, Fourier transform infrared （FTIR） spectroscopy, scanning electron microscopy （SEM） and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate （PHRR）, total heat release （THR） and mass loss rate （MLR） greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.     

Effect of Molecular Structure on the GasPermeability of Cellulose Aliphatate Esters简

In this work, four kinds of cellulose aliphatate esters, cellulose acetate （CA）, cellulose propionate （CP）, cellulose butyrate （CB） and cellulose acetate butyrate （CAB） are synthesized by the homogeneous acylation reactions in cellulose/AmimC1 solutions. These cellulose aliphatate esters are used to prepare gas separation membranes and the effects of molecular structure, such as substituent type, degree of substitution （DS） and distribution of substituents, on the gas permeability are studied. For CAs, as the DS increases, their gas permeabilities for all five gases （02, N2, CH4, CO and CO2） increase, and the ideal permselectivity significantly increases first and then slightly decreases. At similar DS value, the homogenously synthesized CA （distribution order of acetate substituent： C6 〉 C3 〉 C2） is superior to the heterogeneously synthesized CA （distribution order of acetate substituent： C3 〉 C2 〉 C6） in gas separation. With the increase of chain length of aliphatate substituents from acetate to propionate, and to butyrate, the gas permeability of cellulose aliphatate esters gradually increases. The cellulose mixed ester CAB with short acetate groups and relatively long butyrate groups exhibits higher gas permeability or better permselectivity than individual CA or CB via the alteration of the DS of two substituents.     

离子液体[BMIM]PF6中铬的电沉积行为简

以一氯丁烷、N-甲基咪唑和KPF6为原料,合成了1-丁基-3-甲基咪唑六氟磷酸盐离子液体([BMIM]PF6),用红外光谱(IR)对产物进行了结构分析. 用循环伏安法测试该离子液体在85 ℃下的电化学窗口为4.7 V. 考察了[BMIM]PF6-Cr(Ⅲ)电解液的电化学行为,结果表明,在85 ℃下Cr(Ⅲ)的还原过程是受扩散控制的一步还原不可逆过程,Cr(Ⅲ)的传递系数α=0.023,阴极扩散系数D0=1.142×10-6 cm2/s. 在85 ℃和-1.5 V条件下,用恒电势法在铜片上电沉积Cr(Ⅲ),并通过扫描电子显微镜(SEM)观察了铜片上镀层的表面结构,发现该镀层呈颗粒状,且颗粒的体积随沉积时间的延长而增大. X射线能量色散谱(EDS) 和X射线粉末衍射(XRD)测试结果表明,该镀层为无定形的金属铬.     

High Photocatalytic Properties of Zinc OxideNanoparticles with Amidoximated BacterialCellulose Nanofibers as Templates简

The freshly prepared water-wet amidoximated bacterial cellulose （Am-BC） serves as an effective nanoreactor to synthesis zinc oxide nanoparticles by in situ polyol method. The obtained ZnO/Am-BC nanocomposites have been characterized by field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD）, Fourier transformed infrared spectroscopy （FTIR） and thermogravimetric analysis （TGA）. The influence of the zinc acetate concentration on the morphologies and size ofZnO nanoparticles and the possible formation mechanism were discussed. The results indicated that uniform ZnO nanoparticles were homogeneously anchored on the Am-BC nanofibers through strong interaction between the hydroxyl and amino groups of Am-BC and ZnO nanoparticles. The loading content of ZnO nanoparticles is higher using Am-BC as a template than using the unmodified bacterial cellulose. The resultant nanocomposite synthesized at 0.05 wt% shows a high photocatalytic activity （92%） in the degradation of methyl orange.     

Infrared spectroscopy of N-methylacetamide in water from high-level QM/MM calculations简

The infrared(IR) spectra of the N-methylacetamide molecule in water are calculated by using the MD simulation with high-level QM/MM corrections. The B3LYP and MP2 levels with 6-311++G** basis set are used for the QM region, respectively. Our results show all IR spectra at the B3LYP level are well consistent with the corresponding MP2 results. A dynamical charge fluctuation is observed for each atom along the simulation trajectories due to the electrostatic polarization(EP) effects from surrounding solvent environment. We find that the QM/MM corrected IR spectra satisfactorily reproduce the experimental vibrational features of amide I–III modes.     

Morphology and Phase Composition ofGelatin-Starch Blends简

Morphology and phase compositions of different starch-gelatin blends were investigated by various microscopes: optical, SEM and synchrotron FTIR microscopy. A high amylose(80%) corn starch, grafted with hydroxypropyl to enhance flexibilty and hydrophilicity, and plasticized by poly(ethylene glycol)(PEG), was used in this work. SEM revealed that the surface became smoother after adding PEG. Optical microscopy observation revealed that compatibility between gelatin and starch was improved by adding PEG. An FTIR beam focused on a 5 μm× 5 μm detection area by the micro-spectroscope was used to map chemical composition. The ratio of areas of the saccharide bands(1180–953 cm 1) and the amide I and II bands(1750–1483 cm 1) was used to monitor the relative distributions of the two components in the blends. The FTIR maps indicated that gelatin constituted the continuous phase up to 80% of starch content. All of the FTIR spectra showed contributions from both starch and gelatin absorptions, therefore indicating that complete demixing with pure starch and gelatin domains did not occur. The PEG improved the compatibility of the gelatin-starch blends.     

Anodic polymerization of dithienosilole and electroluminescent properties of the resulting polymer

Anodic oxidation of 2,6-bis(trimethylsilyl)-4,4-di(p-tolyl)dithienosilole gave a dark orange solid polymer with a small band gap. The spectral analysis of the polymer indicated that decomposition of the dithienosilole ring system had competed the polymerization to an extent. This, however, could be suppressed by optimizing the reaction conditions. Applications of the spin-coated polymer films to electroluminescent materials are described.     

Size dependence of transition temperature in polymer nanowires

We studied the effect of changing temperature on the mechanical properties of nanosized poly(methyl methacrylate) wires fabricated by two-photon fabrication. At around room temperature, the nanowires showed a transition temperature where the shear modulus suddenly changed. This transition temperature was observed to decrease more than 40 K by decreasing the radius of the nanowires from 450 to 150 nm. This size is several times larger in nanowires than reported values of polymer thin film thickness showing a depression of the glass transition temperature.     

Hydrothermal synthesis and their catalytic properties of manganite nanowires

La_0.5Sr_0.5MnO₃ nanowires and nanoparticles were synthesized by the hydrothermal and citrate methods, respectively. The samples were characterized by TEM, HRTEM, XRD, ICP and N₂ adsorption, etc. The formation mechanism of the nanowires was proposed and discussed. Further, the stabilities and catalytic activities of La_0.5Sr_0.5MnO₃ nanowires for CH₄ combustion were evaluated and compared with those of the nanoparticles. The results showed that the particle morphology had a significant effect on the properties of the catalysts. After running at a high temperature for a long duration, the nanowires showed a higher stability and a higher activity, compared with the nanoparticles. Their different stabilities were ascribed to the different surface energies (particle sizes), as well as to the different geometric packing models.     

Highly visible-light luminescence properties of the carboxyl-functionalized short and ultrashort MWNTs

Luminescence of the short multiwalled carbon nanotubes (MWNTs) conjugated with carboxylic acid groups has been studied. The results show that the carboxyl-functionalized short MWNTs could emit luminescence and the emission peak appears at 500 nm with a corresponding optimal excitation wavelength centering at 310 nm. When the short MWNTs are filtered through 0.15 μm polytetrafluoroethylene (PTFE) membrane, the ultrashort MWNTs are obtained from the filtrate. An interesting feature for the ultrashort MWNTs is that the emission intensity is strengthened and the peak is slightly blue shifted to 460 nm. This result indicates that the luminescence properties of MWNTs are strongly affected by the tube length. After chemical oxidization cutting, defects and carboxylic acid groups at the tube end and/or sidewall can be produced; the more shorten of MWNTs, the better dispersion and carboxylic passivation of the nanotubes, and the more intense luminescence emissions. The broad emissions are logically attributed to the trapping of excitation energy by defect sites in the carboxyl-functionalized nanotube structure.     

First-principles study of structural and electronic properties of gallium based nanowires

Structural stability and electronic properties of GaX (X = N, P, As and Sb) nanowires have been investigated using first-principles based density function theory approach. Out of linear, zigzag, square and hexagon shaped configuration, the square shaped geometry is energetically most stable. The computation of lattice parameters, bulk modulus and pressure derivatives for these Ga based nanowires observes the highest bulk modulus for hexagonal shaped GaN nanowire amongst all, suggest the mechanical strength of this geometry. Electronic band structures analysis shows the semiconducting as well as metallic behavior of these nanowires.     

Calcination-temperature-dependent gas-sensing properties of mesoporous α-Fe2O3 nanowires as ethanol sensors

The mesoporous α-Fe₂O₃ nanowires (NWs) were successfully synthesized by changing the calcination temperature from 550 to 750 °C (marked NWs-550, NWs-650 and NWs-750) via using SBA-15 silica as the hard templates with the nanocasting method. The characterization results indicated that the bandgap of the as-prepared samples hardly changed and the high BET surface areas changed a little with the calcination temperature from 550 to 750 °C. Mesoporous α-Fe₂O₃ NWs had been found to possess the remarkable gas-sensing performance to ethanol gas. The gas-sensing behavior indicated that α-Fe₂O₃ NWs-650 exhibited the higher response than that of α-Fe₂O₃ NWs-550 and α-Fe₂O₃ NWs-750. The calcination-temperature-dependent gas-sensing properties were mainly attributed to the competition of surface defects and body defects by the crystallization temperature. The lower calcination temperature could create more surface defects to improve the gas-sensing response, while the higher temperature would reduce the body defect and make the charge carriers transport easily. As the result, the suitable calcination temperature was desired to optimize the defects of nanostructures to improve the gas sensitivity.     

Side-chain substituent effects on green luminescence of terbium activated hybrid xerogels

We have reported the synthesis of three chemical bonded hybrid materials based on silica matrices composed of terbium ions and aromatic acid derivatives. Of significant importance, ligand 1 was grafted with three long alkyl chains and the as-derived hybrid 1 exhibited attracting green luminescence in solid matrices which is much stronger than ligand 2 which does not bear aliphatic chains. All the fluorescence spectra, quantum yields, and time-resolved spectra proved that the side chains influence for the effective sensitization of terbium ions.     

The effects of La doping on luminescence properties of PbWO4 single crystal

X-ray-excited luminescence (XEL), thermoluminescence (TL), photoluminescence under excitation of UV light and X-ray photoelectron spectroscopy (XPS) measurements were conducted on PbWO₄ (PWO) single crystals doped with La³⁺ at a series of concentration levels. With the increase of doping levels, the intensity of PWO in the XEL or the excitation-emission spectra was found to decrease accordingly, especially in the case of heavy doping. TL peaks in the range from room temperature to 200°C disappeared after the doping with La³⁺. A splitting of the La3d XPS peak in the heavy La³⁺-doped samples was observed and proposed to be responsible for that. At a high doping level, La³⁺ would occupy W-sites besides Pb-sites and thus induce a self-compensation via pairs [(La_W³⁺)″′−(La_Pb³⁺)^•]−(V_O)^•• or clusters [3(La_Pb³⁺)^•−(La_W³⁺)″′], where nonradiative recombination was previously reported to occur. The mechanism of the influence on luminescence was also discussed in this paper.     

Optical properties of bis(cyclopentadienyl)magnesium: excimer-type luminescence of the bis(cyclopentadienyl) ligand frame

The electronic spectra of solid MgCp₂ (Cp = cyclopentadienyl) show features which indicate the presence of intramolecular interligand interactions. The fluorescence of MgCp₂ (λ_max = 363 nm) undergoes a considerable Stokes shift which is apparently caused by a bonding attraction between both Cp rings in the excited state. An additional phosphorescence of the (Cp⁻)₂ fragment (λ_max = 535 nm) appears at 77 K.     

Synthesis of immobilized TiO2 nanowires by anodic oxidation and their gas phase photocatalytic properties

In this paper, anodic oxidation method was successfully employed to the direct growth of immobilized TiO₂ nanowires on titanium foil in ethylene glycol electrolyte solution contained HF and water. The morphologies of the TiO₂ nanowires could be tuned by changing the content of HF and water. The structures, morphologies and optical properties of TiO₂ nanowires were characterized by SEM, XRD, UV–vis and PL. It was found that the nanowires originally grew from the splitting of TiO₂ nanotubes. The gas phase photocatalytic activities were investigated by photodegradation of gaseous toluene under UV irradiation, and irregular TiO₂ nanowires showed the best photocatalytic ability.