Poly(1,1′-binaphthol butyl ether) prepared by solid-state oxidative coupling polymerization and their nanospheres via the reprecipitation method

Polymer Bulletin - Poly(1,1′-binaphthol butyl ether)s have successfully been synthesized by solid-state oxidative polymerization of 1,1′-binaphthol butyl ether with FeCl3 as oxidant for...     

Cross‐Linking of Sulfonated Poly(ether ether ketone) by Thermal Treatment: How Does the Reaction Occur?

The cross‐link reaction between macromolecular chains of sulfonated poly(ether ether ketone) (SPEEK) by thermal treatment above 150 °C in presence of dimethylsulfoxide (DMSO) is investigated by various techniques, including elemental analysis, acid‐base titration, infrared spectroscopy, water uptake (WU) measurements, and thermogravimetry. The conditions of thermal treatment are analyzed. The cross‐linking reaction occurs in at least three more or less activated and deactivated positions with different activation energies, leading to different time dependencies of the cross‐link reaction. The role of residual solvent DMSO is studied particularly: the cross‐linking depends significantly on the amount of solvent in the membranes. Implications on WU and thermal stability are of particular importance for the development of high performance proton‐conducting membranes.     

Experimental measurement and modelling with Aspen Plus® of the phase behaviour of supercritical CO2 + (n-dodecane + 1-decanol + 3,7-dimethyl-1-octanol)

Experimental phase equilibrium data for the systems CO₂ + n-dodecane, CO₂ + 1-decanol and CO₂ + 3,7-dimethyl-1-octanol were used to determine values for binary interaction parameters for use in the RK-ASPEN thermodynamic model in Aspen Plus^®. Bubble and dew point data of the mixtures CO₂ + (n-dodecane + 1-decanol), CO₂ + (n-dodecane + 3,7-dimethyl-1-octanol), CO₂ + (1-decanol + 3,7-dimethyl-1-octanol) and CO₂ + (n-dodecane + 1-decanol + 3,7-dimethyl-1-octanol) were measured experimentally in a static synthetic view cell, and compared to the data predicted by the RK-ASPEN model. The model predicted the phase equilibrium data reasonably well in the low solute concentration region; significant deviation of model predictions from experimental data occurred in the mixture critical and high solute concentration regions due to the exclusion of solute–solute interaction parameters in the model. Distribution coefficients and separation factors were determined for the multi-component mixture and separation of the alkane from the alcohol mixture with a supercritical fluid extraction process was found to be possible.     

Modeling of facilitated transport of Cr(III) using (RNH3+HSO4−) ionic liquid and pseudo-emulsion hollow fiber strip dispersion (PEHFSD) technology

The permeation of chromium (III) using PEHFSD technology and the ionic liquid (RNH₃⁺HSO₄^?), formed by reaction of the primary amine PRIMENE JMT and sulphuric acid, dissolved in n-decane as mobile carrier has been investigated. The alkaline feed solution containing Cr(III) was passed through the tube side, and pseudo-emulsions of the ionic liquid + n-decane + n-decanol and sulphuric acid were passed through the shell side in counter-current mode and using a single hollow fiber module for extraction and stripping. In this advanced membrane technology, the aqueous acidic strip solution is dispersed in the organic membrane solution in a tank with an impeller stirrer to form a strip dispersion. The pseudo-emulsion phase is circulated from the tank to the membrane module to provide a constant supply of the organic solution to the membrane micropores. Factors affecting chromium permeability, such as hydrodynamic conditions, carrier concentration in the organic phase, metal and NaOH concentrations in the feed phase, have been analyzed. A model is reported describing the transport mechanism, whereas the experimental data are quantitatively explained by mathematical equations describing the rate of transport. Different rate-controlling processes take place as long as the metal transport occurs.     

Piezoelectric properties and phase transition temperatures of the solid solution of (1 − x)(Bi0.5Na0.5)TiO3–xSrTiO3

The phase diagram of (1 ? x)(Bi_0.5Na_0.5)TiO₃–xSrTiO₃ was completed and investigations on polarization and strain in this system were carried out. (1 ? x)(Bi_0.5Na_0.5)TiO₃–xSrTiO₃-ceramics were prepared by conventional mixed oxide processing. The depolarization temperature (T_d), the temperature of the rhombohedral–tetragonal phase transition (T_r–t) and the Curie temperature (T_m) were determined by measuring the temperature dependence of the relative permittivity. All solid solutions of (1 ? x)(Bi_0.5Na_0.5)TiO₃–xSrTiO₃ show relaxor behavior (A-site relaxor). From XRD-measurements a broad maximum of the lattice parameter can be observed around x = 0.5 but no structural evidence for a morphotropic phase boundary was found. SEM-analysis revealed a decrease of the grain size for increasing SrTiO₃-content. At room temperature a maximum of strain of about 0.29% was found at x = 0.25 which coincides with a transition from a ferroelectric to an antiferroelectric phase. The temperature dependence of the displacement indicates an additional contribution from a structural transition (rhombohedral–tetragonal), which would be of certain relevance for the existence of a morphotropic phase boundary.     

MLCT interaction in [Rh(II)2(CO3)4]4 −( x L)

Complexes of the type [Rh^II₂(CO₃)₄(H₂O)L]^n − with L = N-methylpyrazinium⁺ and 1-heptyl-4-(4-pyridinyl)pyridinium⁺ cations display intense long-wavelength (Rh(II) to L) MLCT absorptions. With L = H₂O, MLCT absorptions are not identified, but the photoreactivity of the complex in aqueous solution supports the assumption that (Rh(II) to CO₃^2 −) MLCT excited states are accessible. Upon irradiation with white light, Rh(II) is photooxidized while carbonate is reduced to CO. The efficiency of this photolysis is very low. However, the occurrence of this photoredox reaction is, nevertheless, of general interest with regard to the photochemical reduction of CO₂.     

The novel ligand 4′-phenyl-3,2′:6′,3′′-terpyridine (L) and the supramolecular structure of the dinuclear complex [Zn2(μ-L)(acac)4] · H2O (acac = acetylacetonato)

The new terpyridyl ligand 4′-phenyl-3,2′:6′,3′′-terpyridine (L) reacts with Zn(acac)₂ to produce the dizinc complex [Zn₂(μ-L)(acac)₄] · H₂O (1) (acac = acetylacetonato). The analysis of the crystal structure of this zero-dimensional (0D) complex shows the existence of two Zn(acac)₂ centers bridged symmetrically by one μ-L ligand. The key role played by the acac and L ligands and the guest water molecule allows the generation of a series of intermolecular hydrogen bonds of the O–H/O, C–H/O and C–H/π type which give raise to a 3D supramolecular array. The observed C–H/π interactions are so widespread that all the π-rings present in the structure, viz., those belonging to the L ligand as well as the acetylacetonato chelate rings, participate as hydrogen bond acceptors.     

Etherification of n-butanol to di-n-butyl ether over H3PMo12 − xWxO40 (x = 0, 3, 6, 9, 12) Keggin and H6P2Mo18 − xWxO62 (x = 0, 3, 9, 15, 18) Wells–Dawson heteropolyacid catalysts

Etherification of n-butanol to di-n-butyl ether was carried out over H₃PMo_12 − xW_xO₄₀ (x = 0, 3, 6, 9, 12) Keggin and H₆P₂Mo_18 − xW_xO₆₂ (x = 0, 3, 9, 15, 18) Wells–Dawson heteropolyacid (HPA) catalysts. Acid strength of H₃PMo_12 − xW_xO₄₀ Keggin and H₆P₂Mo_18 − xW_xO₆₂ Wells–Dawson HPA catalysts was determined by NH₃-TPD (temperature-programmed desorption) measurements. The correlations between desorption peak temperature (acid strength) of the HPA catalysts and catalytic activity revealed that conversion of n-butanol and yield for di-n-butyl ether increased with increasing acid strength of the catalysts, regardless of the identity of HPA catalysts (without HPA structural sensitivity).     

Light scattering behavior and the kinetics of pressure-induced phase separation in solutions of poly(ε-caprolactone) in acetone + CO2 binary fluid mixtures

The miscibility and the kinetics of pressure-induced phase separation in solutions of poly(ε-caprolactone) (PCL) in acetone + CO₂ binary fluid mixtures have been studied at pressures up to 28 MPa and temperatures up to 410 K using a unique high pressure view-cell equipped with a dual set of pistons and dual set of sapphire windows. One set of the windows separated by 25.4 mm allows the assessment of the phase state and is used to monitor the transmitted light intensities. The second set of windows separated by 50 μm is used to monitor the scattered light intensities over a wide range of scattering vector q (from 0.35 to 4 μm⁻¹) which allows the assessment of the mechanism of phase separation. Investigations have been carried out for a wide range of polymer concentrations, from 2.0 to 34.9 wt%, while holding the acetone-to-CO₂ (wt:wt) ratio in each solution at a constant value of 2:1. The dual set of pistons that are employed which are synchronized and motorized create a churn-like action in the cell insuring effective mixing, even at the high polymer concentrations by translating the cell content across a magnetically-coupled rotating mixer impeller. The piston actions assure also that the solution is effectively introduced into the narrow gap between the scattering windows, and refreshed. The solutions at off-critical concentrations undergo pressure-induced phase separation via nucleation and growth mechanism which shows circular symmetric patterns in their light scattering patterns. For these solutions, the Debye–Bueche type scattering function was used to analyze the domain size of the new phase that forms and develops after a pressure quench. The phase separation in solutions at or near the critical polymer concentrations (9.0–15.0 wt%) proceeds via spinodal decomposition which is characterized by the formation and evolution of the spinodal ring patterns corresponding to a maximum in the angular variation of the scattered light intensities. The results in early stage of the spinodal decomposition were described by the linearized Cahn theory. The variation of the scattered light intensity maximum I_m and its location in scattering vectors q_m with time in the later stage of the spinodal decomposition obey power-law scaling according to I_m ∼ t^β and q_m ∼ t^−α. The results for the 9.0 and 12.0 wt% solutions show that β/α changes its value from β/α > 3 to β/α ≈ 3 with time, indicating the progression of the spinodal decomposition from intermediate to late stage.     

Luminescence of [ReI(L–L)(CO)3Cl] with L–L = lumazine and folic acid

The complexes [Re^I (L–L)(CO)₃Cl] with L–L = lumazine and folic acid were prepared and their electronic spectra were measured. The free ligands L–L, as well as both complexes, show an emission which is attributed to the fluorescence of L–L. This luminescence is apparently facilitated by excited state proton transfer.     

Catalytic performance of NO oxidation over LaMeO3 (Me = Mn,Fe, Co) perovskite prepared by the sol–gel method

The catalytic performance of LaMeO₃ (Me = Mn, Fe, Co) perovskite prepared by a sol–gel method was studied. These catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption (BET), H₂ temperature programmed reduction (TPR), NO temperature programmed desorption (TPD) and CO–O₂ pulse. LaCoO₃ exhibited the best activity than that of LaFeO₃ and LaMnO₃ even after hydrothermal ageing. The activity sequence is in accordance with the reducibility of the samples. The activated oxygen species and adsorbed NO play key roles in the NO oxidation reaction.     

High dielectric Al2O3-(20–30 wt%) HDPE composites processed via cold sintering

In the present work, the dielectric properties of cold sintered alumina (Al₂O₃) reinforced with 20–30 wt% HDPE composite was investigated. The Al₂O₃-HDPE composites were successfully processed via cold sintering at extremely low temperature in the range of 80–120 °C for 120 min with the application of uniaxial pressure of 500 MPa under vacuum. In fact, cold sintering is a promising method to consolidate ceramic-polymer composites with very large difference in melting points and other thermo-physical/chemical properties. In the present work, high dielectric constant (ε’) of 11.73 and low dielectric loss (tanδ) of 0.0076 measured for Cold Sintering Processed (CSPed) Al₂O₃-20HDPE and a little low ε’ of 9.13 and low tanδ of 0.0066 was evident for CSPed-Al₂O₃-30HDPE at 1 MHz. Such differences in the dielectric properties of the Al₂O₃-20,30 HDPE composites depend on the crystallite size, dangling bond density and microstrain of the materials. Increase in ε’ with temperature is noticed for CSPed-A20H. Moreover, for CSPed-A20H at 1 MHz the temperature variation of dielectric constant (TCC) of 186.94 ppm/°C (or 0.018694 %/°C) was estimated and it reflects a marginal variation of ε’ with temperature. The coefficient of thermal expansion (CTE) of 87.25 × 10⁻⁶ °C⁻¹ and 109.3 × 10⁻⁶ °C⁻¹ was estimated for CSPed-A20H and CSPed-A30H, respectively. Overall, the cold sintered Al₂O₃-20HDPE composites exhibited comparable or better dielectric properties than Al₂O₃ based materials (as reported in the literature) processed by conventional sintering or cold sintering processes.     

Heat-insulating properties of hollow Al2O3–ZrO2(CeO2)fibers fabricated using pampas grass as the template

Al₂O₃–ZrO₂(CeO₂) ceramic fibers have good heat insulation and high-temperature resistance. Pampas grass is a large perennial grass, or a natural fiber, with a hollow structure that can improve the heat insulation of the fiber by changing its heat transfer mode. This study introduces a method for the preparation of biomorphic Al₂O₃–ZrO₂(CeO₂) fibers with a hollow structure and a double-layer-tube structure using the pampas grass as thetemplate. Hollow ceramic fibers with good thermal insulation properties were prepared by soaking the pampas grass in ZrOCl₂, Ce(NO₃)₃, and AlCl₃ solutions before sintering them at high temperatures. When the zirconia doping ratio was 11 mol%, the biomorphic fiber with a double-layer-tube structure was prepared. The biomorphic fibers inherited the hollow structure of the pampas grass and retained the template fiber'scharacteristics of excellent continuity and a high degree of hollowness, whichdecreased the thermal conductivity of the fibers.     

Evaluation of the homogeneity in Pb(Zr,Ti)O3–zirconia composites prepared by the hetero-agglomeration of precursors using the Voronoi-diagram approach

Hetero-agglomeration of precursor particles was employed to achieve a homogeneous distribution of tetragonal zirconia (TZ) grains within a lead zirconate titanate (PZT) ceramic matrix. The surface charge of the zirconia particles in the aqueous suspension was modified by the addition of citric acid. At pH 5, the citric-acid-modified TZ particles were negatively charged, while the PZT particles were positively charged, which led to the agglomeration of the two types of particles. The homogeneity of the TZ distribution in the PZT–TZ ceramic composites prepared from the hetero-agglomerated particles was evaluated using Voronoi-diagram analyses. The results showed that the homogeneity of the composites prepared using the citric-acid-modified TZ particles was higher than in the case where the TZ particles were not modified. The curves for the crack-growth resistance were also determined in order to investigate the impact of particle homogeneity on the fracture behavior.     

Determination of the initial heat treatment temperature in the two-step sintering of xAl–ZnO (x = 1, 2, and 3 wt.%)

The application of a two-step sintering route successfully decreased the sintering temperature of Al-doped ZnO transparent conducting oxide target. The two-step sintering consisted of initial heat treatment (IHT) at 800–1000 °C under mild (<2 MPa) external pressure, and pressureless final sintering at 1250–1350 °C in a separate furnace. The optimum IHTs for effective densification depended on the Al doping. The 800 °C IHT was effective for 1 wt.% Al doping, and the 1000 °C IHT, for 3 wt.% Al doping. As a result of the effective IHT, the volume of the micron sized pore decreased with the fragmentation into submicron pores. This suggests that cohesion of the secondary particles occurred during the effective IHT. The IHT temperature for achieving cohesion increased in the 3 wt.% Al doping. The criterion for determining the IHT in the two-step sintering was identified as the minimum temperature at which the cohesion of secondary particles can be achieved.     

Effect of plastics substrate on phase separation behavior and adhesion for RSi(OC2H5)3–Si(OC2H5)4 coatings prepared by sol–gel process

Three functional siliconalkoxides (RSi(OC₂H₅)₃, RTES), phenyltriethoxysilane (PhTES), methyltriethoxysilane (MeTES), and 1,4-bis(triethoxysilyl)benzene (BTEB)–tetraethoxysilane (Si(OC₂H₅)₄, TEOS) coatings [xA?(100?x)TEOS (x=0–80, mol%), A=PhTES, MeTES, BTEB] were prepared by sol–gel process, and the effects of plastics substrates on both the distribution of organic component in the coatings and its adhesion on plastics substrates were discussed. Polyethylene terephthalate (PET) and polycarbonate (PC) with phenyl group and polyethylene (PE), polypropylene (PP) and polyvinylchloride (PVC) without phenyl group were employed as plastics substrates. The distribution of organic component was monitored by total reflection (ATR) fourier transform infrared (FTIR) measurements. Before the solidification of the coating sol, the organic component for good adhesion migrated on coatings/substrate interface side by the interaction between organic component and substrate. This interaction may be caused by π/π electron interaction, CH₃/π electron interaction and CH₃/CH₃ van der Waals interaction. The migration of phenyl group on plastics substrate with phenyl group was larger than that on plastics substrate without phenyl group, while the migration of methyl group on plastics substrate without phenyl group was larger than that on plastics' substrates with phenyl group. Thus, the chemical structure of substrate affected phase separation behavior in the coatings. Adhesion of PhTES–TEOS and BTEB–TEOS coatings on PET and PC increased drastically at larger than x=60. On the other hand, no adhesion was observed for all the MeTES–TEOS coatings.     

Experimental and mathematical modeling of Cr(Ⅵ) removal using nano-magnetic Fe_3O_4-coated perlite from the liquid phase

Modification of perlite using nano-magnetic iron oxide was implemented to produce nano-magneticFe_3O_4-coated perlite composite(Fe_3O_4/Perlite). The prepared composite was characterized using Scanning Electron Microscopy, Fourier-Transform Infrared spectroscopy and Powder X-ray Fluorescence. The potentiality of both perlite and Fe_3O_4/Perlite composite to eliminate Cr(VI) from the environmentally relevant water was investigated.The influence of main factors which could affect the adsorption was studied including; pH of medium, shaking time and Cr(VI) ions concentration. The experimental outcome demonstrated that the modification of perlite by nano-magnetic Fe_3O_4 showed a significantly enhanced Cr(VI) removal efficiency relative to that of unmodified perlite. From the kinetic studies, the experimental data fitted well with the pseudo-second-order model. Moreover, it proposes that Langmuir isotherm is more adequate than the Freundlich isotherm for both perlite and modified perlite. The results recommended that Fe_3O_4/Perlite composite had a great potential as an economic and efficient adsorbent of Cr(VI) from contaminated water, which has huge application potential.     

Enhanced “overall” ionic conductivity in Li1+xAlxTi2−x(PO4)3 (0.3 ≤ x ≤ 0.7) ceramics prepared from sol-gel powders by spark plasma sintering

The Li_1+xAl_xTi_2?x(PO₄)₃ (LATPx) series displays the highest “bulk” reported conductivity, but a much lower “overall” contribution, that changes with the powder preparation and sintering conditions. In this work, the preparation of LATPx ceramics is discussed, by using the sol-gel technique for powders synthesis and mild spark plasma (SPS) for ceramics sintering at 800 °C. An “overall” conductivity ~ 2.10^?3 Ω^?1 cm^?1 was obtained for the x = 0.4 composition, that was the result of a high “bulk” conductivity, an optimized microstructure and almost full density, in absence of micro-cracks, with a small content of secondary phases and clean grain boundaries. Fast-ion ceramics prepared by SPS are good candidates for solid electrolytes in all solid state batteries (ASSB).