Anisotropic ionic conductivity of lithium-doped sulfonated PBI

The conductivity study results of lithium-doped sulfonated PBI, a conjugated rigid rod polymer, poly[(1,7-dihydrobenzo[1,2-d:4,5-d′]dimidazole-2,6-diyl)-2-(2-sulfo)-p-phenylene], derivatized with pendants of propane sulfonate Li⁺ ionomer are reported. The room-temperature DC four-probe conductivity parallel to the surface of cast films was as large as 8.3 × 10⁻³ S/cm. Similar measurements with an eight-probe configuration showed no difference between bulk and surface conductivity. The ionic nature of the conductivity was indicated by constant voltage depletion experiments and by secondary ion mass spectroscopy measurements of the residues near the electrodes. The DC two-probe conductivity measured transverse to the sample surface was three to four orders of magnitude smaller than longitudinal conductivity, while the AC two-probe conductivity was even less. Electron microscopy indicated that the films had a layered structure parallel to the surfaces. This structural anisotropy was confirmed by refractive index values obtained from wave-guide experiments and by wide angle X-ray scattering. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2925–2933, 1997     

n-型掺杂反式聚乙炔导电性能各向异性研究

根据固体能带理论，用量子化学ＥＨＭＯ／ ＣＯ 方法，计算了高取向反式聚乙炔及其ｎ－ 型掺杂态（掺杂Ｌｉ，Ｎａ，Ｋ） 的二维能带结构，首次从能隙与带宽角度讨论了聚乙炔经ｎ－ 型掺杂呈现的导电性能的各向异性．研究表明：平行和垂直于分子链方向的电导率之比（σ∥／σ⊥） 取决于这两个方向上能隙和带宽的大小；掺杂后σ∥／σ⊥下降，其原因是掺杂剂在聚乙炔链间架起了一个“浮桥”，使链间耦合作用增强．理论计算与实验结果一致     

Anisotropic electrical conductivity of drawn elastomeric ionene–TCNQ salts

Elastomeric ionene–TCNQ salts with favorable electrical, mechanical, and processing characteristics were drawn mechanically. The electrical conductivity parallel and perpendicular to the drawing axis was investigated. Correlation between anisotropic conductivity and the change in microstructure was discussed. The resistivity ρ at 25°C of the simple salt (EI-TCNQ₀) and the complex salt (EI-TCNQ_0.5) were on the order of 10⁵ and 10² Ω cm, respectively. In the drawn TCNQ salts, the ρ parallel to the drawing axis increased greatly; on the other hand, the ρ perpendicular to this axis increased slightly or was similar to the ρ of the undrawn TCNQ salts. The anisotropy in the ρ of EI-TCNQ_0.5 between the two directions reached 40 times. The activation energy also increased in the direction parallel to the drawing axis. In the undrawn TCNQ salts, the continuous conduction paths exist isotropically. With drawing, the continuous conduction paths, particularly in the direction parallel to the drawing axis, break or make a structural change. The anisotropic conductivity disappeared with time in EI-TCNQ₀; however, it was present in EI-TCNQ_0.5 even after 200 days under ambient conditions.     

ZrCuSiAs: A “filled” PbFCl type

ZrCuSiAs is tetragonal, space group $\text{P4}\text{nmm}\text{, a = 3.6736, c = 9.5712}$Å, Z = 2. The structure is a “filled” PbFCl type, or it may alternatively be regarded as a tetragonally distorted MnCu₂Al (Heusler) structure. HfCuSiAs is iso-structural. Bonding in PbFCl-related structures is discussed.     

Anisotropic conductivity of undoped and [FeCl4]-doped trans-polyacetylene

EHMO/CO (crystal orbital) quantum chemical methods were used to calculate the two-dimensional (2D) energy band structures of highly oriented trans-polyacetylene (PA) undoped and doped with [FeCl₄]⁻. The band gaps (E_g) of undoped PA in directions parallel and perpendicular to the oriented direction were 1.195 and 3.040 eV, respectively, and that of doped PA with [FeCl₄]⁻ were 0.0223 and 0.0504 eV, respectively. Based on the calculational results, the changes in conductive properties from undoped PA to [FeCl₄]⁻ doped PA could be interpreted. The conductivity anisotropy ratio σ/σ decreased when PA was doped by [FeCl₄]⁻, because the PA chain and the dopant showed a strong interchain coupling. The theoretical results for undoped and doped PA were in good agreement with the experiment.     

Interlayer water molecules in vanadium pentoxide hydrate. IX. Anisotropic translational diffusion leading to anisotropic ac conductivity

The anisotropy of the dynamic properties of interlayer water molecules along the a and b axes of vanadium pentoxide hydrate, orthorhombic V2O5.nH2O, was studied using quasielastic neutron scattering (QENS) in relation to the anisotropy of the ac conductivity. The QENS spectra were analyzed using a stretched exponential function and a Lorentzian function. Both methods showed that the double-layer water molecules along the b axis are more mobile than those along the a axis. The difference in mobility between the two axes is more pronounced using a Lorentzian function analysis. These facts suggest that the diffusion coefficient of water molecules along the b axis is larger than that along the a axis, which is closely related to the ac conductivity originating from proton hopping. The anisotropy of the dynamic motion of water molecules can be attributed to the shorter b-axis length (b=3.60 A), with respect to the longer and less regular repetition of the atomic arrangements along the a axis (42.34 A).     

Anisotropic viscoelasticity of polymers

A director theory of solutions and melts of flexible-chain polymers that is based on a simple law of anisotropic stress relaxation is developed. A spectral approach is used to study its structure. The simplest equation for the director that describes the dependence of the orientation of anisotropic viscoelastic fluids on shear rate is presented. The most appropriate flows for determining the material properties of polymer fluids with a single preferred direction are discussed. In addition, a new classification of anisotropic fluids is proposed.     

Anisotropic agarose gels

Agarose hydrogels deswell reversibly over a wide range of concentration. Two types of deswelling measurements are considered here, isotropic and uniaxial. We describe some of the properties of the gels observed in the deswollen state. In both the isotropic and uniaxial geometry, the swelling pressure varies approximately as the square of the concentration.     

Anisotropic solutions of methylol cellulose

Methylol cellulose solutions in dimethylsulfoxide exhibit a viscosity maximum at 18% w/v followed by a minimum at 20%, as is characteristic of lyotropic liquid crystals. The biphasic solutions exhibit areas of clear and cloudy appearance. The latter are birefringent. The highly anisotropic solutions are uniformly briefringent and in the 25–33% w/v concentration region they are brightly colored. The optical rotations of the mesomorphic phases are high, indicating a cholesteric structure. The sign of the optical rotation depends on the solution concentration and at high concentrations (25+% w/v) varies with the area of the solution viewed.     

Anisotropic assembly of Ag nanoprisms

The Ag nanoprisms with controlled arrangements show distinct optical, crystallographic, and surface-enhanced Raman scattering properties depending on their orientation in the assemblies, demonstrating that the controlled assembly of anisotropic nanostructures can be utilized as a powerful tool for studying their physicochemical properties and for the creation of new classes of functional materials.     

Anisotropic effective core potentials

We present a convenient method for accounting for the anisotropy of partially filled d shells that are incorporated in effective core potentials by including the leading anisotropy term of the d-type electron density, which is the quadrupole moment, as an electrostatic potential energy operator in the model Hamiltonian. We present sample calculations on the cobalt hydride and dicobalt systems. We find the quadrupole anisotropy to have a very large effect in the distance regime of CoH. In the dicobalt system, which has a relatively long internuclear distance, the quadrupole anisotropy shifts the equilibrium bond length by nearly 0.02 bohr.     

Anisotropic nanoparticles of precise microstructure polyolefins

Nanoparticles of precisely branched polyethylenes possess a distinct oblate shape resulting from a crystalline lamella in the particle as revealed by SAXS and TEM, and display controllable and well-behaved thermal behaviour.     

Anisotropic rotation of spin-probes in polymers

The observed change in the ESR spectra of a nitroxide spin-probe as it passes through the transition >T_g found in amorphous polymers is explained in terms of a change in the anisotropic rotation of the probe. The degree of anisotropy factor ? is calculated for various polymers and probes, and shows the most marked change with Tempol Benzoate (I) in atactic polypropylene and plasticized polystyrene. Results for a steroid nitroxide probe are also presented.     

Anisotropic etching of silicon in hydrazine

This paper contains a detailed discussion of the practical issues related to the anisotropic etching of single crystal silicon using a 5050 hydrazinewater solution. Characteristics of the etchant, etching reactor design, etch procedures, safety precautions, etch rate data for typical samples and appropriate etch-masks are among the topic discussed. The etching process is carried out in a atmospheric reflux reactor, continuously purged with nitrogen. The etch rate of (100) silicon at 115°C in this hydrazine solution is nearly 3 μm/min, which is much higher than that of ethylenediaminepyrocatecholwater (EDP) solutions. Silicon dioxide, silicon nitride and most metallic thin films, except aluminium, can be used to mask the etching process. The etch rate is reduced significantly in highly-boron-doped silicon; a boron concentration of 1.5 × 10²⁰ cm⁻³ practically stops the etch. The use of the hydrazine solution for micromachining thin silicon diaphragms, cantilevers and fibers is demonstrated.     

Engineered Anisotropic Fluids of Rare-Earth Nanomaterials

The self-assembly of inorganic nanoparticles into well-ordered structures in the absence of solvents is generally hindered by van der Waals forces, leading to random aggregates between them. To address the problem, we functionalized rigid rare-earth (RE) nanoparticles with a layer of flexible polymers by electrostatic complexation. Consequently, an ordered and solvent-free liquid crystal (LC) state of RE nanoparticles was realized. The RE nanomaterials including nanospheres, nanorods, nanodiscs, microprisms, and nanowires all show a typical nematic LC phase with one-dimensional orientational order, while their microstructures strongly depend on the particles’ shape and size. Interestingly, the solvent-free thermotropic LCs possess an extremely wide temperature range from −40 °C to 200 °C. The intrinsic ordering and fluidity endow anisotropic luminescence properties in the system of shearing-aligned RE LCs, offering potential applications in anisotropic optical micro-devices.     

Polyelectrolyte conductivity

Using the de Gennes scaling model for the configuration of a polyelectrolyte chain in semidilute solution, we construct a simple model of AC conductivity for semidilute solutions of strongly charged polyelectrolytes without added salt. We compare the predictions of this model with literature data and new data on two polyelectrolytes with very different affinities for water. The sodium salt of sulfonated polystyrene in water is a hydrophobic polyelectrolyte (the uncharged monomer does not dissolve in water), where the chain is locally collapsed. The sodium salt of poly(2-acrylamido-2-methylpropanesulfonate), is a much more hydrophilic polyelectrolyte, making the chain quite expanded locally. The model describes the conductivity of both cases reasonably for concentrations below 10⁻² M (mol of monomer per liter). Deviations between experiment and theory at higher concentrations lead us to conclude that counterion condensation decreases as concentration is increased. This is qualitatively consistent with the experimental observation that the dielectric constant of the polyelectrolyte solution increases as polyelectrolyte is added. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2951–2960, 1997     

Electrodeless conductivity

Electrodeless conductivity is a technique for measuring the concentration of electrolytes in solution and utilizes a probe consisting of two toroids in close proximity, both of which are immersed in the solution. In special cases, the toroids may be mounted externally on insulated pipes carrying the solution. One toroid radiates an alternating electric field in the audiofrequency range and the other acts as a receiver to pick up the small current induced by the ions moving in a conducting loop of solution. Coatings which would foul contacting electrodes, such as suspensions, precipitates or oil, have little or no effect. Applications are chiefly to continuous measurement in the chemical processing industries, including pulp and paper, mining and heavy chemical production. The principles and practical details of the method are reviewed and cell-diameter, wall, and temperature effects are discussed.     

Anisotropic wetting on checkerboard-patterned surfaces

A series of surfaces with microscale checkerboard patterns consisting of continuous central lines and discontinuous lateral lines were fabricated. The surface wetting properties of these checkerboard patterns were found to be anisotropic. The central continuous lines were found to have a strong influence on the dynamic wetting properties and moving trajectories of the water droplets. The droplets move more easily in the direction parallel to the central continuous lines and less easily in the direction perpendicular to the central continuous lines. Meanwhile, the droplets' moving path tends to incline toward the central continuous lines from a tilting direction. When the microsurface was modified with a layer of nanowire, the surface wettability was found to be isotropic and superhydrophobic.     

New gadolinium polyselenide GdSe<Subscript>1.89(6)</Subscript> in the PbFCl matlockite structure type

Optimal growth conditions for GdSe_1.85 crystals are found by the thermodynamic simulation of the Gd–Se–I system. The obtained data are used to grow GdSe_1.85 crystals by the vapor transport method using iodine as a transport agent. The grown crystals are identified by microprobe and powder XRD analyses. The structure is determined by the single crystal XRD analysis and the composition is refined. The crystal structure is in general typical of the structures of REM polychalcogenides, however, the unit cell represents the metric type unknown previously: a = 4.0562(2) Å, b = 8.1065(5) Å, c = 9.2489(5) Å, α = 115.9990(10)°, β = 90.000(2)°, γ = 89.9750(10)°, V = 273.34(3) Å3, Z = 4, d_calc = 7.659 g/cm³, space group Pb11. The experimental material for the single crystal XRD analysis is obtained on an automated Bruker X8 APEX diffractometer (MoK _α radiation, graphite monochromator, CCD detector resolution 1024×1024 pixel, distance to the detector L = 50 mm, rotation about the φ axis 15 min) by the standard procedure, 2274 measured reflections, out of them 1523 independent (R(int) = 0.0352), R factor [I > 2σ(I)] = 0.0517, R factor (all measured) = 0.0694).