Pure gas and vapor permeation properties of poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] (PTMSDPA) and its desilylated analog, poly[diphenylacetylene] (PDPA)

The permeabilities of He, H₂, N₂, O₂, CO₂, CH₄, C₂H₆, C₃H₈, and n-C₄H₁₀ in poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] (PTMSDPA) and poly[diphenylacetylene] (PDPA) are presented and compared to those of poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and polysulfone. Like PTMSP, PTMSDPA, a disubstituted glassy acetylene-based polymer, exhibits higher permeabilities to organic vapors than to permanent gases due to its rigid polyacetylene backbone and bulky side groups, which provide a relatively high fractional free volume (FFV) value of 0.26. Desilylation was performed on PTMSDPA. The resulting material, PDPA, is totally insoluble in common organic solvents, so it has much higher chemical resistance than PTMSDPA. Additionally, due to its insolubility in polymerization solvents, desilylation provides the only known route to high molar mass PDPA. The FFV of the resulting membrane (PDPA) is reduced by approximately 12% relative to that of PTMSDPA. This leads to a decrease in gas permeability values and selectivity of organic vapors relative to nitrogen. For example, the oxygen permeability is reduced from 1200 to 500 Barrers upon desilylation. The pure gas selectivities decrease from 9 to 3 for n-C₄H₁₀/N₂ and from 26 to 9 for C₃H₈/N₂.     

Hybrid materials for immobilization of MP-11 catalyst

Microperoxidase-11(MP-11) has been immobilized for the first time in hybrid periodic mesoporous organosilica (PMO) materials and in a nano-crystalline metal organic framework (MOF). Microperoxidase-11 was physically absorbed from solution into the periodic mesoporous organosilica MBS and functionalized derivatives of MBS as well as in the 3-dimensional [Cu(OOC–C₆H₄–C₆H₄–COO)·? C₆H₁₂N₂] _n metal organic framework. The conversion of Amplex^? UltraRed and methylene blue to their respective oxidation products by immobilized MP-11 was determined.     

Monolayers and mixed-layers on copper towards corrosion protection

In order to improve the protection abilities of (3-mercaptopropy)trimethoxysilane (MPTS) self-assembled monolayers on copper surfaces, mixed monolayers have been formed successfully by successive immersions in MPTS and in n-dodecanethiol (DT). A newly synthesised molecule, (11-mercaptoundecyl)trimethoxysilane (MUTS), has also been employed to form a thicker organic film on copper surfaces and, thereby, enhance the inhibitory action of the coating. The grafting has been confirmed by X-ray photoelectron spectroscopy (XPS), polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS) and water contact angle. The protective efficiency of each protective organic film has been evidenced by cyclic voltammetry (CV) and polarization curve measurements (CP). It was shown that the MUTS and unhydrolyzed MPTS/DT films exhibited significant corrosion protection properties.     

Capacitive and textural characteristics of hydrous manganese oxide prepared by anodic deposition

The amorphous hydrous manganese oxide (denoted as a-MnO_x·nH₂O) was anodically deposited from the MnSO₄ solutions of various pH values. The capacitive characteristics and stability of this oxide without and with annealing in air for 2 h up to 400 °C were systematically investigated in aqueous electrolytes through means of cyclic voltammetry (CV) and the constant-current charge-discharge method. The redox properties of a-MnO_x·nH₂O were strongly affected by the electrolytes employed and this oxide exhibited ideally capacitive behavior in 0.1 M Na₂SO₄ and 0.3 M KCl. The stability of this amorphous hydrous oxide was enhanced by the annealing treatment while its capacitance was gradually decreased with increasing the annealing temperature. The amorphous structure and surface morphologies of a-MnO_x·nH₂O with annealing at different temperatures were, respectively, examined in terms of the X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) photographs. The oxidation states of these a-MnO_x·nH₂O deposits were studied by X-ray photoelectron spectroscopy (XPS).     

Modification of copper with self-assembled organic coatings

Self-assembled monolayers of n-alkanethiols (CH₃(CH₂)_n−1SH; n = 12 and 18) were prepared on a copper surface, and the quality and protection efficiency of resulting coatings against aqueous corrosion of copper were investigated. A combination of physical (scanning electron microscopy, energy dispersive X-ray spectroscopy and contact angle measurements) and electrochemical (cyclic voltammetry and impedance spectrometry) methods was used to correlate the structure of the coatings with their barrier properties during exposures in an aqueous solution. Impedance results reveal that the coatings behave almost like an ideal dielectric, with a resistance of several MΩ cm² and a coating capacitance that agree well with the value calculated according to the theory of dielectrics. Protection efficiency of chemisorbed alkanethiol coatings determined from dc and ac measurements were above 99%.     

The key factor determining the anodic deposition of vanadium oxides

This work demonstrates that anodic deposition of vanadium oxide (denoted as VO_x·nH₂O) can be considered as the chemical co-precipitation of V⁵⁺ and V⁴⁺ oxy-/hydroxyl species and the accumulation of V⁵⁺ species at the vicinity of electrode surface is the key factor for the successful anodic deposition of VO_x·nH₂O at a potential much more negative than the equilibrium potential of the oxygen evolution reaction (OER). The results of in situ UV-vis spectra show that the V⁴⁺/V⁵⁺ ratio near the electrode surface can be controlled by varying the applied potential, leading to different, three-dimensional (3D) nanostructures of VO_x·nH₂O. The accumulation of V⁵⁺ species due to V⁴⁺ oxidation at potentials ≥0.4 V (vs. Ag/AgCl) has been found to be very similar to the phenomenon by adding H₂O₂ in the deposition solution. The X-ray photoelectron spectroscopic (XPS) results show that all VO_x·nH₂O deposits can be considered as aggregates consisting of mixed V⁵⁺ and V⁴⁺ oxy-/hydroxyl species with the mean oxidation state significantly increasing with the applied electrode potential.     

Pure and mixed gas CH4 and n-C4H10 sorption and dilation in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ sorption and dilation in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures ranging from −20 to 35 °C. The presence of n-C₄H₁₀ in the mixture considerably reduces CH₄ solubility. For example, CH₄ solubility (in the limit of zero CH₄ fugacity) at 25°C decreases from 4.0 (pure gas) to 0.78 cm³(STP)/(cm³ polymer atm) in the presence of n-C₄H₁₀ at an activity of 0.60. At −20 °C, CH₄ solubility decreases by almost an order of magnitude, from 10.2 (pure gas) to 1.22 cm³(STP)/(cm³ polymer atm) in the presence of n-C₄H₁₀ at an activity of 0.61. In contrast, n-C₄H₁₀ mixture sorption properties are not measurably affected by the presence of CH₄. The dual mode sorption model parameters for CH₄ and n-C₄H₁₀ in PTMSP were determined from pure and mixed gas sorption measurements, and this model can adequately describe the sorption data. The n-C₄H₁₀/CH₄ mixed gas solubility selectivity in PTMSP decreases as temperature increases and as n-C₄H₁₀ activity increases. For example, at 25 °C, the n-C₄H₁₀/CH₄ solubility selectivity decreases from 250 to 120 as n-C₄H₁₀ activity increases from 0.02 to 0.25. At −20 °C and an n-C₄H₁₀ activity of 0.24, the n-C₄H₁₀/CH₄ solubility selectivity is 590. Penetrant-induced volume dilation of PTMSP can be adequately modeled by assuming that all swelling is caused by penetrant molecules sorbed in the polymer's dense equilibrium region (i.e., the Henry's law region) during sorption. However, the best fit partial molar volumes in the Henry's law region for the dilation data are considerably lower than the penetrant partial molar volumes in liquids, suggesting that further theoretical efforts are needed to develop predictive models of volume dilation in high free volume glassy polymers.     

Pure and mixed gas CH4 and n-C4H10 permeability and diffusivity in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ permeability coefficients in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures from −20 to 35 °C. CH₄ partial pressures range from 1.1 to 14.6 atm, and n-C₄H₁₀ partial pressures range from 0.02 to 1.8 atm. CH₄ permeability decreases with increasing n-C₄H₁₀ upstream activity (f/f_sat) in the feed. For example, at −20 °C, CH₄ permeability decreases by more than an order of magnitude, from 52,000 to 1700 Barrer, as n-C₄H₁₀ activity increases from 0 to 0.73. In contrast, n-C₄H₁₀ mixed gas permeability is essentially unaffected by the presence of CH₄. The depression of CH₄ permeability in mixtures is a result of competitive sorption and blocking effects, which reduce both CH₄ mixture solubility and diffusivity, respectively. Diffusion coefficients of n-C₄H₁₀ and CH₄ in mixtures were calculated from mixture permeability and mixture solubility data. The CH₄ concentration-averaged diffusion coefficient generally decreases as n-C₄H₁₀ activity increases. On the other hand, the n-C₄H₁₀ diffusion coefficient is essentially unaffected by the presence of CH₄. Pure and mixed gas activation energies of permeation and diffusion of CH₄ and n-C₄H₁₀ are reported. The mixed gas n-C₄H₁₀/CH₄ permeability selectivity increases with increasing n-C₄H₁₀ activity and decreasing temperature, and it is higher than pure gas estimates would suggest. Mixture diffusivity selectivity also increases with increasing n-C₄H₁₀ activity. The difference between pure and mixed gas permeability selectivity arises from both solubility and diffusivity effects. The dual mode mixed gas permeability model describes the mixture permeability data reasonably well for n-C₄H₁₀. However, the model must be modified to accurately describe the methane data by accounting for the decrease in methane diffusivity due to the presence of n-C₄H₁₀ (i.e., blocking). Even though the penetrant concentrations are rather significant at some of the conditions considered, no evidence is observed for phenomena such as multicomponent coupling that would require a model more complex than the binary form of Fick's law. That is, Fick's law in its simplest form adequately describes the experimental data.     

Redox Properties and Catalytic Oxidation Activities of Polyatom-Substituted H n PW11M1O40 (M = V, Nb, Ta, and W) Keggin Heteropolyacid Catalysts

Redox properties and catalytic oxidation activities of polyatom-substituted H _n PW₁₁M₁O₄₀ (M = V, Nb, Ta, and W) Keggin heteropolyacids (HPAs) were examined. Reduction potentials and UV–visible absorption edge energies of H _n PW₁₁M₁O₄₀ (M = V, Nb, Ta, and W) HPA catalysts in solution were determined by an electrochemical method and UV–visible spectroscopy measurements, respectively. It was observed that reduction potentials of H _n PW₁₁M₁O₄₀ (M = V, Nb, Ta, and W) HPA catalysts increased and UV–visible absorption edge energies of the HPA catalysts decreased with decreasing electronegativity of substituted polyatom. It was also found that the lower absorption edge energy corresponded to the higher reduction potential of the HPA catalyst. Vapor-phase oxidation of benzyl alcohol was carried out as a model reaction to probe the redox properties of H _n PW₁₁M₁O₄₀ (M = V, Nb, Ta, and W) HPA catalysts. Yield for benzaldehyde increased with increasing reduction potential and with decreasing absorption edge energy of the HPA catalyst, and in turn, with decreasing electronegativity of substituted polyatom. Reduction potential of H _n PW₁₁M₁O₄₀ (M = V, Nb, Ta, and W) HPA catalysts measured by an electrochemical method and absorption edge energy of the HPA catalysts measured by UV–visible spectroscopy could be utilized as a probe of oxidation catalysis of the HPA catalysts.     

Thinopyrum ponticum Chromatin-Integrated Wheat Genome Shows Salt-Tolerance at Germination Stage

A wild wheatgrass, Thinopyrum ponticum (2n = 10x = 70), which exhibits substantially higher levels of salt tolerance than cultivated wheat, was employed to transfer its salt tolerance to common wheat by means of wide hybridization. A highly salt-tolerant wheat line S148 (2n = 42) was obtained from the BC₃F₂ progenies between Triticum aestivum (2n = 42) and Th. ponticum. In the cross of S148 × salt-sensitive wheat variety Chinese Spring, the BC₄F₂ seeds at germination stage segregated into a ratio of 3 salt tolerant to 1 salt sensitive, indicating that the salt tolerance was conferred by a dominant gene block. Genomic in situ hybridization analysis revealed that S148 had a single pair of Th. ponticum–T. aestivum translocated chromosomes bearing the salt-tolerance. This is an initial step of molecular breeding for salt-tolerant wheat.     

Fluorous Surface‐Active Distannoxane Catalysts

Fluorous distannoxanes (XR^f₂SnOSnR^f₂X)₂⋅n H₂O (R_f=C₆F₁₃C₂H₄) ( 1 : X=C₈F₁₇SO₃, n=10; 4 : X=Cl, n=0) ( 1 ) catalyze the Mukaiyama aldol reaction and the allylation of aldehydes with tetraallyltin at room temperature in fluorous/organic biphasic solvent systems, in which the reactions proceed more rapidly than in a single organic or fluorous solvent. Due to the unique surface activity of 1 , the catalyst, organic substrate(s), and reagent(s) are distributed in both organic and fluorous phases to facilitate smooth reactions. Upon dilution with toluene after the reaction, the catalyst concentrates to the fluorous phase, while the organic substances migrate to the organic phase to effect facile catalyst recovery and recycling. By virtue of such a unique solvophilicity, a new version of fluorous biphase technology has been developed.     

Synthesis and crystal structure of three dimensional complex from copper(II) and 1,2,4,5-benzenetetracarboxylate

A copper(II) complex {[Cu(H₂btc) (H₂O)₃]₂(H₄btc)(C₅H₁₁N)₂ · 3H₂O}_n (1) has been synthesized and characterized structurally (H₄btc=1,2,4,5-benzenetetracarboxylic acid). Open channels were formed and can accommodate piperidine molecules. TGA data show that guest water and piperidine molecules are lost at 130 °C.     

Synthesis and structure of the n = 4 member of the framework aluminium alkylenediphosphonate series Al2[O3PC n H2n PO3](H2O)2F2

We report here the solvothermal synthesis and crystal structure of the hybrid inorganic-organic framework material Al₂[O₃PC₄H₈PO₃](H₂O)₂F₂?2H₂O (monoclinic, 1P2₁ /m, a = 4.961(2) Å, b = 11.930(5) Å, c = 10.727(5) Å, β = 93.972(6)^°, Z = 2, R(F, F ² > 2σ) = 0.094, R _w(F ², all data) = 0.262), the third member of the Al₂[O₃PC _n H_{2 n} PO₃](H₂O)₂F₂ framework series. The structure is formed from corrugated chains of corner-sharing AlO₄F₂ octahedra in which alternating AlO₄F₂ octahedra contain two fluorine atoms in a trans or a cis configuration. The diphosphonate groups link the chains together through Al-O-P-O-Al bridges and through the butyl groups to form a three-dimensional framework structure containing a one-dimensional channel system consisting of one type of channel only. The channels contain four extra-framework water molecules per unit cell. The formation of this member of the series shows that the form of the alkyl chain can successfully define the number of channel types and the channel length in this hybrid framework system.     

Scale-up of a fixed bed electrochemical reactor consisting of parallel screen electrode used for p-aminophenol production

The behavior of a fixed bed consisting of amalgamated copper screens has been investigated for the electrolytic reduction of nitrobenzene to p-aminophenol under potentiostatic condition (controlled potential). The preparative electrolysis of nitrobenzene was carried out using supporting electrolytes consisting of 2 M H₂SO₄ in a solution of 50% 2-propanol/50% water (v/v). The criterion for scale-up (?_n) was determined through application of one-dimensional model. The polarization curves that describe the reduction of nitrobenzene to p-aminophenol were obtained experimentally by using a pilot scale for different nitrobenzene concentrations and flow rates of catholyte.It was found that the effectiveness factor (?_n) increases with increasing flow rate, and decreasing nitrobenzene concentration. An optimum thickness of bed equal to 0.6 cm was obtained, in which the effectiveness factor not less than 0.588, to ensure a well distribution of current and potential.     

The morphology of poly(aryl-ether-ether-ketone)

The morphology and related properties are described for the aromatic thermoplastic poly(aryl-ether-ether-ketone) (PEEK) [C₆H₄OC₆H₄OC₆H₄CO]_n. Topics covered include crystallinity, crystallization and melting behaviour, Iamellar thickness and spherulitic structure. The data are used to derive the following material parameters $\text{T1}{}_{\mathrm{<mtext>m</mtext>}}\text{= 395°}\text{C}$, σ_e = 49 erg cm^?2, σ_s = 38 erg cm^? and ΔH_F = 130 kJ kg^?1. PEEK is closely analogous to poly(ethylene terephthalate) in its crystallization behaviour except that the main transitions occur about 75°C higher.     

Structural behaviour of molecular alloys: n-pentacontane (n-C50H102)-n-pentacosane (n-C25H52); n-pentacontane (n-C50H102)-n-tricosane (n-C23H48) at room temperature

This paper displays a study of binary mixtures of n-alkanes whose ratio of chain length is around two. The systems composed of n-tricosane (n-C₂₃H₄₈)-n-pentacontane (n-C₅₀H₁₀₂) and n-pentacosane (n-C₂₅H₅₂)-n-pentacontane (n-C₅₀H₁₀₂) have been studied by means of X-ray analyses. These latter, performed at room temperature, showed in both cases, the existence of a large domain where the phases characteristic of each pure component coexist. These mixtures obey Kravchenko's rule relative to the solubility of the n-alkanes according to the chain length of each component. The mixtures studied do not form an intermediate solid solution. In other words, there is no particular arrangement of the shorter molecules inside the crystallographic unit of the longer.     

Hydrothermal synthesis,crystal structure,spectroscopy, electrochemistry and antimycobacterial evaluation of the copper (II) ciprofloxacin complex: [Cu(cf)2(BF4)2]·6H2O

The hydrothermal reaction of ciprofloxacin (1) with Cu(BF₄)₂·6H₂O yields a copper complex having a molecular formula, [Cu(cf)₂(BF₄)₂]·6H₂O (cf = ciprofloxacin), which is characterized by spectroscopic and electrochemical measurements as well as single crystal X-ray studies [a=9.1079(13), b=9.6112(16), c=11.4542(18) Å, α=90.518 (19)°, β=99.160 (18)°, γ=93.315 (19)°, P1bar, Z=1]. The F₂O₄ donor atom set forms a (4+2) distorted octahedral geometry around the central copper atom; which has a highly facile copper redox couple (+0.23 V). The copper conjugate exhibits a significant enhancement in the antitubercular activity probably arising out of its rapid intracellular reduction leading to oxygen activation, which is detrimental to the mycobacteria.     

Direct Hydroxylation of Benzene to Phenol with Molecular Oxygen over Pyridine-modified Vanadium-substituted Heteropoly Acids

Pyridine(Py)-modified Keggin-type mono-vanadium-substituted heteropoly acids (Py _n PMo₁₁V, n = 1–4) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were characterized by FT-IR. Among various catalysts, Py₄PMo₁₁V exhibited the highest catalytic activity (yield of phenol 9.0%) with the high selectivity for phenol, without observing the formation of catechol, hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent, oxidant and reducing reagent, respectively. The influences of the reaction temperature, the pressure of oxygen, the amount of ascorbic acid, the amount of catalyst, and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation. Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H₄PMo₁₁VO₄₀), mostly because the organic π electrons in the hydrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and thus dramatically modify the redox properties.     

Electrochemical and spectroelectrochemical characterization of meso-tetra-alkyl porphyrins

A series of three meso-tetra-alkyl porphyrins (H₂TAPs) were synthesised and their electrochemical properties were studied in dichloromethane containing either tetra-butyl ammonium perclorate (TBAP) or tetra-butyl ammonium hexafluorophosphate TBA(PF₆) as supporting electrolyte (SE) by cyclic voltammetry and in situ UV/vis spectroelectrochemistry. Values of E_1/2 for the recorded four redox processes of these porphyrins and of the meso-tetra-phenyl porphyrin (H₂TPP) on glassy carbon and platinum were measured and compared. The redox data collected on the first oxidation and the first reduction processes predict that the value of Δ(LUMO − HOMO) for the H₂TAPs is lower than for meso-tetra-phenyl porphyrin and, therefore, that the first Q band of the electronic spectra of the H₂TAPs is red shifted relatively to the same band in the spectrum of H₂TPP; this shift was indeed found. The second oxidation process of the H₂TAPs is influenced by the supporting electrolyte used and the dication then formed is consumed by an irreversible chemical reaction. The species produced in this reaction is irreversibly reduced at a considerably lower potential. The electrochemical and spectroelectrochemical data collected are consistent with the occurrence of structural distortion in the macrocycle rings of the H₂TAPs.     

Catalytic effects of NaOH and ZrO2 for partial oxidative gasification of n-hexadecane and lignin in supercritical water☆

Partial oxidative gasification of n-hexadecane (n-C₁₆) and organosolv-lignin (lignin) was studied by use of a batch type reactor in supercritical water: 673 K, 0.52 cm⁻³ of water density (40 MPa of water pressure at 673 K), and 0.3 of O/C ratio for the n-C₁₆ experiments; 673 K, 0.35 cm⁻³ of water density (30 MPa of water pressure at 673 K), and 1.0 of O/C ratio for the lignin experiments. The experiments without O₂ were also conducted for lignin (lignin decomposition). For all the cases (n-C₁₆ partial oxidation, lignin decomposition, lignin partial oxidation), NaOH or zirconia (ZrO₂) was added in the system as catalysts. Through n-C₁₆ studies, the catalytic effect of NaOH and ZrO₂ on partial oxidation in supercritical water were examined. In the case of lignin partial oxidation, we studied the possibility of partial oxidation in supercritical water for gasification technique of wastes. The yield of H₂ from n-C₁₆ and lignin with zirconia was twice as same as that without catalyst at the same condition. The H₂ yield with NaOH was 4 times higher than that without catalyst. Thus, a base catalyst has a positive effect on partial oxidation of n-C₁₆ and lignin to produce H₂. The catalytic effect of NaOH and ZrO₂ was found to be enhancement of decomposition of intermediate (aldehyde and ketone) into CO, through n-C₁₆ studies. In the case of lignin studies, the enhancement of decomposition of the carbonyl compounds by catalytic effect of NaOH and ZrO₂ inhibit char formation and promotes CO and thus H₂ formation.