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971.
The thermal conductivity λ and heat capacity per unit volume of poly(propylene glycol) PPG (0.4 and 4.0 kg·mol−1 in number-average molecular weight) have been measured in the temperature range 150–295 K at pressures up to 2 GPa using the transient hot-wire method. At 295 K and atmospheric pressure, λ = 0.147 W m−1K−1 for PPG (0.4 kg·mol−1) and λ = 0.151 W m−1K−1 for PPG (4.0 kg·mol−1). The temperature dependence of λ is less than 4 × 10−4 W m−1K−2 for both molecular weights. The bulk modulus has been measured in the temperature range 215–295 K up to 1.1 GPa. At atmospheric pressure, the room temperature bulk moduli are 1.97 GPa for PPG (0.4 kg·mol−1) and 1.75 GPa for PPG (4.0 kg·mol−1). These data were used to calculate the volume dependence of $ \lambda ,g\, = - \left( {\frac{{\partial \lambda /\lambda }}{{\partial V/V}}} \right)_T $. At room temperature and atmospheric pressure (liquid phase) we find g = 2.79 for PPG (0.4 kg·mol−1) and g = 2.15 for PPG (4.0 kg·mol−1). The volume dependence of g, (∂g/∂ log V)T varies between −19 to −10 for both molecular weights. Under isochoric conditions, g is nearly independent of temperature. The difference in g between the glassy state and liquid phase is small and just outside the inaccuracy of g of about 8%. The theoretical model for λ by Horrocks and McLaughlin yields an overestimate of g by up to 120%. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 345–355, 1998 相似文献
972.
Vladimir O. Aseyev Stanislav I. Klenin Heikki Tenhu 《Journal of Polymer Science.Polymer Physics》1998,36(7):1107-1114
Samples of a polyelectrolyte poly(methacryloylethyl trimethylammonium methylsulfate), PMETMMS, with molar masses Mw = 22−25 × 106 were examined with viscosity, static light scattering, and conductivity measurements in a water–acetone solvent. Because acetone is a nonsolvent for this polymer the measurements were performed to determine the influence of the solvent composition, the polymer concentration, and the presence of added ions on the conformation of the polyelectrolyte in mixed solvents. The possible influence of a hydrodynamic field on the polymer conformation was also studied. The viscosity of the polymer solutions as a function of polymer concentration, as well as of the solvent composition, was studied using a broad range of shear rates. When the mass fraction of acetone in the solvent, γ, is below 0.5, the solutions show a usual polyelectrolyte behavior. When γ ≥ 0.80, the polymer adopts a compact conformation. This is observed as a decrease of the radius of gyration, Rg, second virial coefficient, A2, the viscosity, and also as a change in the conductivity of the solution. The change in the polymer conformation may be induced also by dilution. When 0.60 ≤ γ < 0.80, a gradual decrease in the polymer concentration leads to a sudden decrease of the reduced viscosity, which indicates a decrease in the particle size. The values of Mw measured by static light scattering were constant in all experiments. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1107–1114, 1998 相似文献
973.
We have studied the temperature variation of conductivity and 1H NMR linewidth of (PEG)xNH4ClO4 (x = 20, 30, 46, 100, 200, & 1000) polymer electrolyte systems. The temperature dependence of the conductivity shows two distinct behaviors, the low temperature VTF dependence crossing over to Arrhenius dependence at higher temperatures. The departure from the VTF behavior is found to be composition dependent. NMR spectra indicate the presence of large fractions of crystalline regions that start to melt around the crossover temperature. We understand the deviation from the VTF behavior as a consequence of this crystalline to elastomer transition. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1201–1209, 1998 相似文献
974.
The selection of a polymer matrix for a conductive blend with polyaniline and para-toluene sulfonic acid (PANI-pTSA) was performed using molecular simulation techniques, both a fast quantitative structure–properties relationship method as a first screening phase followed by atomistic simulation. Using the atomistic simulation method, the solubility parameters and the heat of mixing of each blend were calculated to enable the determination of compatible matrices in blends with PANI-pTSA, which was validated by experimental scanning electron microscopy fractographs. Based on such calculations, polycaprolactone (PCL)/PANI-pTSA phase diagrams were estimated, showing slight miscibility of polydispersed PANI in PCL, particularly the short chains fraction, at the elevated melt processing temperature. It was suggested that this partial miscibility at the elevated temperature might lead to a conductive network morphology of PANI in PCL at room temperature, because of phase separation and precipitation of soluble PANI molecules, upon cooling and solidification of the melt. © 1998 John Wiley & Sons, Ltd. 相似文献
975.
H. Kleinke 《无机化学与普通化学杂志》1998,624(8):1272-1278
The New Antimonides ZrNiSb and HfNiSb: Synthesis, Structure, and Properties in Comparison to ZrCoSb and HfCoSb The antimonides ZrNiSb and HfNiSb were prepared by arc-melting of stoichiometric mixtures of Zr, ZrSb2 and Ni, and Hf, HfSb2 and Ni, respectively. Unlike ZrCoSb and HfCoSb, which form the LiAlSi structure type, ZrNiSb and HfNiSb crystallize in the TiNiSi type. The lattice dimensions are a = 672.7(2) pm, b = 416.43(8) pm, c = 753.8(1) pm, V = 211.16(7) × 106 pm3 for ZrNiSb and a = 662.3(5) pm, b = 413.3(3) pm, c = 746.8(8) pm, V = 204.4(3) × 106 pm3 for HfNiSb (space group Pnma). Whereas no Zr–Zr contacts < 400 pm occur in the structure of ZrCoSb, Zr–Zr bonds are found in the structure of ZrNiSb. This difference is a consequence of the different numbers of valence electrons. The structural differences come along with a drastic change in the electronic structure and in the physical properties: ZrNiSb exhibits metallic behavior, in contrast to the not conducting ZrCoSb. 相似文献
976.
H. Kleinke 《无机化学与普通化学杂志》1998,624(11):1771-1776
ScCoSb: the Most Valence-Electron-Poor Ternary Transition Metal Antimonide MM'Sb with M–M Bonding The antimonide ScCo1–xSb was prepared by arc-melting the elements. ScCoSb crystallizes in the TiNiSi structure type, occurring as a drilling. The lattice parameters are a = 680.62(6) pm, b = 425.65(5) pm, c = 737.77(8) pm, V = 213.74 106 pm3 (space group Pnma, Z = 4). Besides strong Sc–Sb-, Co–Sb-, and Sc–Co bonding, Sc–Sc bonds stabilize the structure to a small extent. The results of Extended Hückel calculations point to metallic properties of ScCoSb, which are confirmed by measurements of the electrical resistivity as a function of temperature. 相似文献
977.
The effect of substrates on the addition polymerization of 1,4-benzenedithiol (BDT) to 1,4-diethynylbenzene (DEB) in the solid state and the electronic properties of the polymers obtained were studied. As the substrate polymer sheets, for instance, PET (poly (ethylene terephthalate)) sheet, ON-6 (oriented nylon-6) sheet and so on having surface free energies Γs from 27.4 to 55.0 erg/cm2 were used. At the monomer sublimation temperature of 60°C, the S wt% (sulfur content) and the cis content of the polymers were not affected by the kind of polymer sheets. However, the molecular weights, M¯n of the polymers polymerized on the polymer sheets were 13,000–30,000, and the values were several times higher than the molecular weight of the polymers polymerized on glass plate. On the other hand, at the sublimation temperature of 82°C, the cis content of the polymers apparently increased with decreasing d-value of the polymer sheets. On X-ray diffraction patterns of monomer mixtures sublimed onto polymer sheets, the diffraction intensities and the diffraction peak positions were concerned with the d-value of the polymer sheets. Using polymer sheets, the diffraction peak intensities of the monomer mixture at 7.73 and 7.58 Å decreased compared with those on glass plate. In contrast, the peak at 3.65 Å, which is a negligibly small peak on glass plate, obviously increased. However, as the d-value of the polymer sheets (PET 3.45 Å; OPP (oriented polypropylene) 5.2 Å) increased, the diffraction peak intensities at 7.73 Å and 7.58 Å gradually increased and the diffraction peak intensity at 3.65 Å gradually decreased. The parallel electrical conductivities (σ||) toward the layered structural polymer on PET, ON-6 and glass plate under air atmosphere were 10−7, 10−9 and 10−11 S/cm, respectively. Under a reduced pressure of 10−3 mmHg, the σ|| values of each polymer lowered by one or two orders of magnitude. On the other hand, the σ|| values of the nonlayered structural polymers under air atmosphere were about 10−11–10−12 S/cm and were independent of the substrates. Even under a reduced pressure of 10−3 mmHg, the σ|| values hardly changed and remained at 10−11–10−12 S/cm. The vertical electrical conductivities (σ⟂) of the layered structural polymers on conductive PET sheet coated by indium tin oxide or NESA glass plates were independent of the substrates and were 10−14 S/cm under air atmosphere. The σ⟂ values of the nonlayered structural polymers also exhibited the same values. The reversible change of the amount of the layered structural polymer on PET sheet was also caused by irradiation of the photo-light which is the effective wavelength for the phase transition of the polymers mounted on glass plate. The σ|| value of the layered structural polymer on ON-6 sheet reversibly changed with the amount of the layer structure controlled by the photo-light, that is, the σ|| increased up to about one order of magnitude by the photo-light at 545.6 nm. On the other hand, the || decreased to about one order of magnitude by the photo-light at 539.6 nm. Anisotropic conductivity with respect to σ|| and σ⟂, and oxygen doping mechanisms were discussed in relation to the layer structure of polymers. © 1997 John Wiley & Sons, Ltd. 相似文献
978.
Magnetic resonance measurements, including nuclear magnetic resonance T1 and T1 and electron paramagnetic resonance T1 and T2e relaxation times are presented for polyanilines prepared according to a modification of the conventional synthesis and doping methods, showing a conductivity higher than that of standard HCl-polyaniline polymers. The results, obtained as a function of the doping rate, are interpreted in terms of one-dimensional diffusive motions of spin and charge carriers. High anisotropy in the spin diffusion rate is found. In the framework of the model of single metallic polymer chains, this leads to the conclusion that in our polyanilines the mechanism of conduction is more markedly one-dimensional. © 1997 John Wiley & Sons, Ltd. 相似文献
979.
The optical and spectral properties of foams and emulsions provide information about their micro-/nanostructures, chemical and time stability and molecular data of their components. Foams and emulsions are collections of different kinds of bubbles or drops with particular properties. A summary of various surfactant and emulsifier types is performed here, as well as an overview of methods for producing foams and emulsions. Absorption, reflectance, and vibrational spectroscopy (Fourier Transform Infrared spectroscopy-FTIR, Raman spectroscopy) studies are detailed in connection with the spectral characterization techniques of colloidal systems. Diffusing Wave Spectroscopy (DWS) data for foams and emulsions are likewise introduced. The utility of spectroscopic approaches has grown as processing power and analysis capabilities have improved. In addition, lasers offer advantages due to the specific properties of the emitted beams which allow focusing on very small volumes and enable accurate, fast, and high spatial resolution sample characterization. Emulsions and foams provide exceptional sensitive bases for measuring low concentrations of molecules down to the level of traces using spectroscopy techniques, thus opening new horizons in microfluidics. 相似文献
980.