The glass temperature of polymer blends

The entropy theory of glasses is used to derive the glass temperature, T_g, of a binary polymer blend in terms of the glass temperatures of the two substituents. The formula is T_g = B₁T_g1 + B₂T_g2, where B_i is the fraction of flexible bonds of substituent i. A bond is flexible if rotation about it changes the shape of the molecule. Bonds in side groups as well as in the backbone are to be counted. This formula assumes that the free volume, taken here to be the volume fraction of empty lattice sites, is the same for each of the three materials. It has no parameters. The above equation expressed in weight fractions, W_i, is (T_g − T_g1)W₁(γ₁/ω₁) + (T_g − T_g2)W₂(γ₂/ω₂) = 0, where ω_i is the weight of a monomer unit and gg_i is the number of flexible bonds per monomer unit. A more general treatment is given. One variation of the more general treatment which expresses the properties of the blend in purely additive terms gives T_g = B₁T_g1 + B₂T_g2 + KB₁B₂(T_g1 − T_g2)(V₀₁ − V₀₂), where V_0i are the free volume fractions of the homopolymers at their glass temperatures and K is a constant. The added term is usually small. The most general form of the equation requires the energy of interaction between the two unlike molecules, which can be estimated by volume measurements on the blend.     

Electrosorption and inhibition properties of p-norborn2-yl phenolate ions at the mercury/solution interface

The electrosorption properties of p-norborn-2-yl phenolate ions in alkaline solutions were investigated by ac polarographic and electrocapillary measurements.

Two adsorption regions were found. At low bulk surfactant concentrations the adsorption at the positively charged electrode (−0.2 E −0.6 V) is predominant while at higher surfactant concentrations the adsorption at the negatively charged electrode (−0.6 E −1.0 V) is more pronounced. At E = −0.40 V the adsorption parameters were determined (a ≈ 2; ΔG°_A = −32.5 ± 1 kJ mol⁻¹. Between −0.6 E −1.0 V one potential of maximum adsorption for all concentrations does not exist and therefore the adsorption parameters could not be calculated.

At E = −0.40 V progressive two-dimensional nucleation with a nucleation order of 3 was observed which corresponds well with the high attraction constant.

The electrode reaction S₂O²⁻₈ + 2e⁻ → 2 SO²⁻₄ is inhibited by norborn-2-yl phenolate ions in the potential range −0.2 E −0.6 V. In the second potential range of capacity decrease the electrode process is much less retarded. At E = −0.40 V, in a similar manner as described for neutral molecules, a linear dependence of the log k_s (k_s apparent rate constant) on ln c_A and π (π = surface film pressure), respectively, has been found.     

Effect of electro-chemical properties of sodium salts of various anions on their diffusional parameters in symmetrical cellulose acetate membranes

A relation was obtained between electro-chemical properties of sodium salts (NaCl, NaBr, and Na₂SO₄), and the thermodynamic property of permeability in symmetrical cellulose acetate membranes, the distribution coefficient K and the kinetic property, the overall diffusion coefficients D. K and D were obtained by the method we proposed using measured unsteady- and steady-state dialysis data. The K values increase with the increase of water content and are in the range of 10⁻² for sodium halides and 10⁻³ for Na₂SO₄. D is found to increase with the increase of the solute concentration, and the extrapolated values of D to zero concentration D⁽⁰⁾ are obtained as 0.015–0.03 μm²/s and increase with the increase of water content in the membrane. D can be divided into the concentration independent diffusion coefficients in the dense part of the membrane D_d and in the porous D_p, applying a two-part (perfect or dense and imperfect or porous) model of the membrane. Contrary to D_d, D_p increases with the increase of W_w and can be correlated as D_p,c = _d exp (γ × W_w). It is shown that the averaged D_d, _D increases with the increase of the quantity of the ionic mobility u of the solutes at infinite dilution divided by valence, and that the parameter γ increases with the increase of the ionic mobility u. The value of K increases slightly with the increase of water content and decreases with the increase of the Flory—Huggins parameter χ. The Flory—Huggins parameter χ is calculated from the measured values of distribution coefficients and data obtained from the literature. And it was found that the gradient of linear decrease of χ (λ_cation) depends on equivalent ionic conductivity of anion of salt, λ_an.     

Walden product, ion-solvent interactions and solvent structure in water-rich mixtures ionic conductances in water-sulfolane, water-acetonitrile and water-dimethylsulfoxide

Conductance measurements are reported for several salts in binary aqueous mixtures containing up to 60 mole % sulfolane, 20 mole % acetonitrile and 20 mole % dimethylsulfoxide. The variations of R = (λ^±₀η₀)_s/(λ^±₀η₀)_w with solvent composition have been compared with those observed in other water-rich mixtures. Alkali cations show R values greater than one with maxima in all the solvent mixtures. This behaviour has been discussed in terms of “sorting”, “averaging” and “steric” effects. Contrary to what happens to alkali cations, halide ions show R values greater or lesser than one according to whether the organic solvent respectively increases or decreases water structure. On these bases we suggest that conductometric behaviour of the halide ions may be indicative of the effect of the cosolvent on the water structure in water-rich mixtures and that DMSO is a water structure breaker.     

Einfluss der säurekonzentration auf die anodische auflosung des indiumamalgams

The effect of HClO₄ concentration on the rate of electrode processes on a stationary indium amalgam electrode in stirred In(ClO₄)₃ solutions at constant ionic strength (3 M NaClO₄) has been investigated. Alongside with the measurement of polarization curves, the exchange current and the true rate of the anodic process of amalgam dissolution (i_a at different potentials (φ) were determined by a radiochemical method. With an increase in the HClO₄ concentration, a sharp decrease in the exchange current is observed; at HClO₄ concentrations below 0.2 M at constant φ, the i_a values are inversely proportional to the HClO₄ concentration. The experimental results are expressed by the equation p] i_a = k[In][H⁺]⁻¹ exp (βφF|RT),

where [In] is the concentration of the indium amalgam. The rate of the cathodic process at constant φ also decreases with a decrease in pH. A hypothesis is advanced according to which partially hydrolysed In(H₂O)₅OH²⁺ ions, rather than In(H₂O)₆³⁺ which are predominant in the solution, participate in the electrode process. The OH⁻ ions, like some other anions, appear to be capable of facilitating the transfer of electrons between the electrode surface and the reacting particle. An analysis of the results obtained (and of data in the literature) shows that partially hydrolysed metal ions play an essential role in electrode processes.     

H4SiW12O40-catalyzed oxidation of nitrobenzene in supercritical water: kinetic and mechanistic aspects

The catalytic effect of a heteropolyacid, H₄SiW₁₂O_40, on nitrobenzene (20 and 30 μM) oxidation in supercritical water was investigated. A capillary flow-through reactor was operated at varying temperatures (T=400–500 °C; P=30.7 MPa) and H₄SiW₁₂O₄₀ concentrations (3.5–34.8 μM) in an attempt to establish global power-law rate expressions for homogenous H₄SiW₁₂O₄₀-catalyzed and uncatalyzed supercritical water oxidation. Oxidation pathways and reaction mechanisms were further examined via primary oxidation product identification and the addition of various hydroxyl radical scavengers (2-propanol, acetone, acetone-d₆, bromide and iodide) to the reaction medium. Under our experimental conditions, nitrobenzene degradation rates were significantly enhanced in the presence of H₄SiW₁₂O₄₀. The major differences in temperature dependence observed between catalyzed and uncatalyzed nitrobenzene oxidation kinetics strongly suggest that the reaction path of H₄SiW₁₂O₄₀-catalyzed supercritical water oxidation (average activation E_a=218 kJ/mol; k=0.015–0.806 s⁻¹ energy for T=440–500 °C; E_a=134 kJ/mol for the temperature range T=470–490 °C) apparently differs from that of uncatalyzed supercritical water oxidation (E_a=212 kJ/mol; k=0.37–6.6 μM s⁻¹). Similar primary oxidation products (i.e. phenol and 2-, 3-, and 4-nitrophenol) were identified for both treatment systems. H₄SiW₁₂O₄₀-catalyzed homogenous nitrobenzene oxidation kinetics was not sensitive to the presence of OH√ scavengers.     

Theory of “Cohesive” vs “Adhesive” Separation in an Adhering System

It is shown that there is limited validitity to the doctrine that true interfacial separation, in an adhering system, is highly improbable. An analysis employing the Griffith-Irwin crack theory yields these results: The important parameters are, difference in elastic moduli, ΔE; differences in g, the energy dissipation per unit crack extension; thickness, Δ₁ or δ₂, of the region where dissipation occurs; and the presence or absence of strong interfacial bonds. If the forces across the interface are appreciably weaker than the cohesive forces in either phase, there is a strong minimum in g at the interface. For flaws of equal size, an interfacial flaw will be the site of initiation of failure. If strong interfacial bonds are present, then if Δg and ΔE have the same sign, failure is most probable, deep within one phase. If Δg and ΔE have opposite signs, failure may be initiated, and may propagate, at a distance δ from the interface, in the phase with lower g. This may be mistaken for weak-boundary layer failure.     

Synthesis and single crystal structure of an AFX-type magnesium aluminophosphate

SAPO-56 (framework type: AFX) has a framework topology slightly different from that of zeolite chabazite (framework type: CHA). While metal substituted aluminophosphate chabazite analogues can be prepared under a variety of experimental conditions with dozens of different amines, the synthesis of SAPO-56 type materials has been more difficult, particularly in non-SAPO compositions. Prior to this work, the growth of large crystals of the AFX-type materials suitable for single crystal diffraction has not been possible in any composition. Here we report the synthesis and single crystal structure of a magnesium aluminophosphate denoted as MAPO-AFX. This represents the first time that the AFX-type topology is made in a metal aluminophosphate composition. The synthesis was accomplished with a novel polyether diamine as the structure-directing agent. Crystal data for MAPO-AFX, (RH₂)_0.10(NH₄)_0.45[Mg_0.65Al_1.35(PO₄)₂](H₂O) where R=O[CH₂CH₂O(CH₂)₃NH₂]₂, space group P-31c (#163), Z=12, MoK radiation, 2θ_max=50°, a=13.8425(6) Å, c=20.204(1) Å, V=3352.7(3) ų, refinement on F², R(F)=7.94% for 131 parameters and 1218 unique reflections with I>2.0σ(I).     

Gas-liquid chromatography study of poly(ethylene oxide)-solvent interactions: A molecular approach to solvation mechanisms

The heats of solution at infinite dilution, ΔH_s, of more than 40 solvents of widely different structure and polarity (from n-hexane to 2,2,2-trifluoroethanol) in liquid poly (ethylene oxide) PEO, derived from gas-liquid chromatography, were quantitatively analysed within the general framework of linear solvation energy relationships: −ΔH_s(kcal mol⁻¹) = 0.48 × 10²⁴P + 1.725μ + 4.29, R(26 solvents) = 0.9566. This linear multiparametric approach allows us to separate the contributions of dispersion-cavitation forces (probe polarizability P), of dipolar interactions (probe dipole moment μ) and of hydrogen bonding (H-bond donating power of the probe measured by the Taft empirical parameter). It affords reliable values for the heat of H-bonding formation between protic probes and PEO. The potential value of such a correlation analysis as a general strategy to quantify solute-polymer interactions in polar systems at a molecular level is emphasized.     

A new tantalum sulfur compound as electrode material for non-aqueous alkali metal batteries

Polycrystalline (PbS)_1.14(TaS₂)₂, a misfit layer sulfide, was used as cathodic material for lithium secondary battery. One molar LiClO₄ in propylene carbonate (PC) was used as electrolyte. The cell could be galvanostatic discharged down to x = 4.6 [Li_x(PbS)_1.14(TaS₂)₂] when the current density was 65 μA cm⁻² and the cell was cycled more than 100 times between 3.5 and 1.5 V at a current density of 260 μA cm⁻². Lattice expansion increased linearly with lithium content and was less than that reported for the Li/TaS₂ system. Chemical diffusion coefficients were determined by a modified version of the galvanostatic intermittent titration technique and they were fairly constant in the composition range 0.2 < x < 1, and an average value of 8.1 × 10⁻¹¹ cm² s⁻¹ was calculated. Sodium intercalation was also accomplished, but the uptake of this ion resulting in a significant lattice expansion compared with that observed for lithium ions. Moreover, a similar dependence of the sodium chemical diffusion coefficient on the composition was observed with an average value of 1.4 × 10⁻¹⁰ cm² s⁻¹, somewhat higher than that of lithium ion. We believe that differences in lattice expansion may be responsible for the differences found in the chemical diffusivity values.     

Microwave dielectric characteristics of ceramics in Mg2SiO4–Zn2SiO4 system

(Mg_1−xZn_x)₂SiO₄ ceramics were prepared and characterized. The densification temperatures of the present ceramics are much lower than those for Mg₂SiO₄ and Zn₂SiO₄ end-members. Small solid solution limits of Zn in Mg₂SiO₄ and Mg in Zn₂SiO₄ are observed, and the bi-phase structure is confirmed in (Mg_1−xZn_x)₂SiO₄ ceramics with x = 0.1–0.9. Even though, it is clear that the Qf value of Zn₂SiO₄ ceramics can be significantly improved together with a suppressed temperature coefficient of resonant frequency τ_f by substituting Mg for Zn. (Mg_0.4Zn_0.6)₂SiO₄ ceramics indicate a good combination of microwave dielectric characteristics: _r = 6.6 Qf = 95,650 GHz, and τ_f = −60 ppm/°C.     

Reptation in polymer blends

Forward recoil spectrometry (FRES) was used to measure the tracer diffusion coefficients D*_PS and D*_PXE of deuterated polystyrene (d-PS) and deuterated poly(xylenyl ether) (d-PXE) chains in high molecular weight protonated blends of these polymers. The D*s were shown to be independent of matrix molecular weights and to decrease as M⁻², where M is the tracer molecular weight, suggesting that the tracer diffusion of both species occurs by reptation. These D*s were used to determine the monomeric friction coefficients ζ_0,PS and ζ_0,PXE of the individual PS and PXE macromolecules as a function of ф, the volume fraction of PS in the PS:PXE blend. Since ζ_0,PSζ_0,PXE at each ф, the rate at which a PS molecule reptates is much greater than that of a PXE molecule, even though both chains are diffusing in identical surroundings. Part of this difference may be due to the difficulty of backbone bond rotation of the PXE molecule. However, even when measured at a constant temperature increment above the glass transition temperature, ζ_0,PS and ζ_0,PXE were observed to be markedly composition dependent. In addition the ratio ζ_0,PS/ζ_0,PXE varied from a maximum of 4 × 10⁻² near ф=0.85 to a minimum of 5 × 10⁻⁵ for ф=0.0. These results show that intramolecular barriers do not solely determine the ζ₀s of the components in this blend. Clearly, the interactions between the diffusing chains and the matrix chains also influence ζ₀.     

(CH3CH[NH3]CH2NH3)1/2·ZnPO4, a zincophosphate analogue of aluminosilicate zeolite thomsonite

The synthesis and structure of (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, an organically templated zincophosphate (ZnPO) analogue of aluminosilicate zeolite thomsonite (THO), are described. The ZnPO framework is built up from an alternating, vertex-sharing, network of ZnO₄ and PO₄ groups (d_av(Zn–O)=1.944 (8) Å, d_av(P–O)=1.535 (9) Å, θ_av(Zn–O–P)=130.5°) involving distinctive 4=1 secondary building units. The 1,2-diammonium propane cations are highly disordered in the [0 0 1] 8-ring channels. Crystal data: (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, M_r=198.42, orthorhombic, space group Pncn (no. 52), a=14.119 (6) Å, b=14.136 (5) Å, c=12.985 (5) Å, V=2591 (3) ų, Z=10, R(F)=0.057, R_w(F)=0.061 (for a twinned crystal).     

The solubility of ettringite at 25°C

Available solubility constants indicate that ettringite should be the stable form of calcium aluminate sulfate hydrate with respect to monosulfate in cement porewater. However, monosulfate is generally present in mature cement pastes, usually in the absence of ettringite. The objectives of this study were to determine the solubility product of ettringite under equilibrium conditions and to examine the solubility data used in predictive thermodynamic models. Solubility products were calculated for ettringite prepared from both supersaturated and undersaturated solutions with a pH range between 10.4 and 13.7. The mean solubility product for ettringite dissolution: Ca₆Al₂O₆(SO₄)₃ · 32H₂O → 6Ca²⁺ + 2Al(OH)₄⁻ + 3SO₄²⁻ + 4OH⁻ + 26H₂O was 10^−44.91, i.e. Log K_sp = -44.91 ± 1.06 (2 S.D.). Activity coefficients were calculated using the specific ion interaction approach. The mean solubility product was close to other values calculated from concentrations reported elsewhere for the solubility of ettringite. As is the case for all solubility products, this value cannot be inserted directly into the databases of other thermodynamic models because of differences in the methods used to calculate activity coefficients and the manner in which ion-pairing is handled by different models. However, raw solubility data are provided for recalculation of the solubility product for use in other models.     

The relationship between the strength of an adhesive bond and the thermodynamic properties of its components

Maximum stability of any system is achieved when its free energy is minimum, in accordance with the second law of thermodynamics. Considering the adhesive bond as a thermodynamic system, it is proposed that the minimum interfacial energy coincides with (1) the maximum strength, and (2) the maximum durability, understood as bond resistance to degradation under environmental attack. The thermodynamic properties of bond components which play a key role in promoting conditions for maximum strength of adhesion have been identified. The general pattern of the relationship: STRENGTH = function (interfacial energy and related parameters), has been developed based on experimental data covering a variety of adhesives and substrates such as metals (steel and aluminium), plastics, ceramics and glass fibre composites. The influence of adhesion promoters (eg, silanes) has also been considered.

It is shown that conditions for maximum strength coincide with the minimum interfacial energy of the system, acquired when the ratio of the surface energy of the substrate, γ₁, to that of the cured adhesive, γ₂ (ie, a = γ₁/γ₂), has a specific value denoted a_MIN. Systems with energy ratios a a_MIN were found to have engineering utility, because the strength deficiency for a >a_MIN was found to be significantly less than for a MIN.     

Synthesis, structure and thermal properties of a novel 3D aluminophosphate UiO-26

The synthesis of a novel 3D aluminophosphate is described. The thermal properties of the material were investigated, and the existence of three high-temperature variants was revealed. The crystal structures of the as-synthesized material (UiO-26-as) and the material existing around 250°C (UiO-26-250) were solved from powder X-ray diffraction data. UiO-26-as with the composition [Al₄O(PO₄)₄(H₂O)]²⁻[NH₃(CH₂)₃NH₃]²⁺ crystallizes in the monoclinic space group P2₁/c (no. 14) with a=19.1912(5), b=9.3470(2), c=9.6375(2) Å and β=92.709(2)°. It exhibits a 3D open framework consisting of connections by PO₄ tetrahedra with AlO₄ tetrahedra, AlO₅ trigonal bipyramids and AlO₅(H₂O) octahedra forming two types of layers stacked along [1 0 0] and connected by Al–O–P bondings. The structure possesses a 1D 10-ring channel system running along [0 0 1], in which doubly protonated 1,3-diaminopropane molecules are located. UiO-26-250 with the composition [Al₄O(PO₄)₄]²⁻[NH₃(CH₂)₃NH₃]²⁺ crystallizes in the monoclinic space group P2₁/c with a=19.2491(4), b=9.27497(20), c=9.70189(20) Å and β=93.7929(17)°. The transformation to UiO-26-250 involves removal of the water molecule which originally is coordinated to aluminum. The rest of the structure remains virtually unchanged. The crystal structures of the two other variants existing around 400 (UiO-26-400) and 600°C (UiO-26-600) remain unknown.     

Insight into solute-solute and solute-solvent interactions of semicarbazide hydrochloride in water and D-glucose/D-sucrose+water solutions at temperatures (293.15 to 318.15) K

The solute-solute and solute-solvent interactions of drug semicarbazide hydrochloride with carbohydrates (D-glucose/D-sucrose) are investigated by using volumetric, viscometric and acoustic properties. The measurements of the densities ρ, ultrasonic speeds u, and viscosities η. of semicarbazide hydrochloride in 5% and 10% D-glucose/D-sucrose+water (w/w) solutions were carried out at temperatures (293.15-318.15) K and at pressure, p=101 kPa. The apparent molar volumes, V_ϕ, limiting apparent molar volumes,V_ϕ°, apparent molar compressibilities, K_{s, ϕ}, limiting apparent molar compressibilities, K_s,ϕ°, partial molar expansibilities, E_ϕ°, transfer volumes, V_ϕ,tr° and transfer compressibilities, K_s,ϕ,tr° have been calculated from the experimental data. The viscosity data were examined by using the Jones-Dole equation and the viscosity A and B coefficients were evaluated. The results are discussed in terms of solute-solute and solute-solvent interactions in these solutions. The structure making/breaking ability of semicarbazide hydrochloride is examined using the sign of temperature derivative of B-coefficient, dB/dT.     

（C5H7N2O2）4（SiMo12O40）的合成、结构及催化氧化碘离子研究

采用常规水溶液法合成了一种新型的有机-无机杂化多金属氧酸盐（C₅H₇N₂O₂）₄（SiMo₁₂O₄₀）（简称SiMo-12）。采用红外光谱（IR）、热重分析（TG）、单晶和粉末X射线衍射（XRD）、元素分析等对SiMo-12进行了表征。以过氧化氢为氧化剂,运用SiMo-12催化碘离子氧化,考察了催化剂用量、氧化剂用量、pH、温度等因素对反应速率的影响。结果表明：该化合物属三斜晶系,P-1空间群,晶胞参数a=1.097 58（4） nm、b=1.144 88（4） nm、c=1.252 66（4） nm、α=64.665（1）°、β=64.804（1）°、γ=83.441（1）°、V=1.282 89（8） nm³、Z=1、R=0.034 0、wR₂=0.079 9。化合物由4个1-咪唑乙酸和一个经典的Keggin型[SiMo₁₂O₄₀]^4-单元组成,有机配体和多金属氧酸阴离子之间通过静电作用、质子转移以及氢键作用沿x轴形成一维链,链与链之间相互平行形成平行于xy面的二维层,层与层之间再通过氢键连接而得到三维网状结构。SiMo-12在催化碘离子氧化中表现出较为优异的催化活性,在c（SiMo-12）=2.0×10^-4 mol/L、c（过氧化氢）=2.0×10^-3 mol/L、pH=1.4、50 ℃条件下反应速率达到2.641 6×10^-5 mol/（L·s）,比未加催化剂时的反应速率提高了1 565倍。     

Analysis of the thermal hysteresis in partially deuterated tryglicine selenate

Dielectric constant data on partially deuterated triglycine selenate (TGSe)_1-x, (DTGSe)_x for x = 0, 0.35, 0.80 show a steady increase of thermal hysteresis ΔT(x) with deuteration, in agreement with previous data by Gesi. In this work we correlate this observed thermal hysteresis with the parameter g(x) = (γ/β)N²μ² obtained from hysteresis loops data, in order to characterize the ferroelectric transition. For x = 0, the transition is close to a tricritical point (g ≌ 1/3) and we see that cooling very slowly through T_c under these quasitricritical conditions results in a very large residual contribution to the dielectric constant at the ferroelectric phase.