Crystallization of Anodic Alumina Membranes Studied by Simultaneous TG-DTA/FTIR

The thermal change of anodic alumina (AA), particularly the exothermic peak followed by the endothermic peak at ca 950°C was studied in detail by mainly using simultaneous TG-DTA/FTIR. The gradual loss of mass up to ca 910°C is attributed to dehydration. When heated at a constant rate by using TG-DTA, an exothermic peak with subsequent endothermic peak is observed at ca 950°C, but the exothermic peak becomes less distinct with decreasing heating rate. It has been found that gaseous SO₂ accompanying a small amount of CO₂ is mainly discharged at this stage. The reaction in this stage can be considered roughly in two schemes. The first scheme can be said collectively as crystallization, in which the migration of S or C trapped inside the crystal lattice of the polycrystalline phase (γ-, δ-, and θ-Al₂O₃, which presumably accompanies a large amount of amorphous or disordered phase) occurs. In the second scheme, the initial polycrystalline (+amorphous) phase crystallizes into a quasi-crystallineγ-Al₂O₃-like metastable phase after amorphization. Conclusively,after the distinct exo- and endothermic reactions, the amorphous phase crystallizes intoγ-Al₂O₃, presumably accompanying small amount of δ-Al₂O₃. It is also found that, when maintained isothermally, the metastable phases undergo transformation into the stable α-Al₂O₃ at 912°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mutual conversion between stretched and contracted helices accompanied by a drastic change in color and spatial structure of poly(phenylacetylene) prepared with a [Rh(nbd)Cl]2‐amine catalyst

The yellow‐colored poly(phenylacetylene), Poly( Y ), is obtained from phenylacetylene using a [Rh(nbd)Cl]₂‐NEt₃ catalyst in ethanol at 25 °C. The color of Poly( Y ) drastically changes into red Poly( R ) or reddish‐black Poly( B ) by immersion in acetylacetone or exposure to chloroform vapor, respectively. Poly( R ) is also created from Poly( B ) by contact with acetylacetone. Poly( Y ) is regenerated from both Poly( R ) and Poly( B ) by reprecipitation from their chloroform solution into methanol. Wide‐angle X‐ray scattering (WAXS) patterns of Poly( Y ) and Poly( R ) correspond to a pseudohexagonal crystal called a columnar as stretched cis‐transoid and contracted cis‐cisoid helices, respectively. These helical diameters and pitch widths obtained from the WAXS measurements are agreed with those of MMFF94 calculation models. The smallest helical pitch width is 3.3 Å for Poly( R ) and Poly( B ). Moreover, information regarding the size and ordering of the vacant space within each polymer is estimated by using ¹²⁹Xe NMR technique. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 752–759     

Lithiosilanes and their application to the synthesis of polysilane dendrimers

An account is given of the preparation and structural investigations of silyllithium compounds, including X-ray and NMR data. This review covers the chemistry of lithiosilanes with alkyl, aryl, functional substituents and lithiooligosilanes with Si---Si bonds. Application of lithiosilanes for the synthesis of polysilane dendritic molecules is also described.     

Enhanced adhesion of copper plating to polyether ether ketone based on active oxygen species generated under ultraviolet irradiation

Polyether ether ketone (PEEK) is a substrate for metal plating to overcome insulation defects and satisfy the increased demands of mechanically robust electronic circuit boards. However, pristine PEEK is hydrophobic; hence, the adhesion between the metal film and PEEK substrate is poor. Therefore, the PEEK surface should be modified to improve hydrophobicity. We have proposed the active oxygen (AOS) treatment under ultraviolet (UV) light as an alternative to a conventional plasma treatment method. Characteristics of the PEEK surfaces obtained by these methods are compared. We explore the effects of reactive-oxygen and UV light exposure time on the PEEK surface modification. The contact angle of water drop on PEEK after the AOS treatment is lower than that of untreated PEEK. Furthermore, COO groups are observed on the PEEK surface after the treatment. Although plasma treatment has the effect of roughening the surface, it is desirable not to roughen the surface for use in electronic circuit boards. Moreover, we have reported the adhesion strength between PEEK and copper plating without surface roughening.     

Large-Field X-ray Imaging at SPring-8 BL20B2

The medium-length (215 m) bending-magnet beamline 20B2 is allocated to medical applications and various X-ray micro imaging techniques (e.g., angiography, computed tomography, phase contrast imaging and diffraction topography) [1 S. Goto, Nuclear Instruments and Methods in Physics Research A 467–468, 682–685 (2001).[Crossref], [Web of Science ®] , [Google Scholar]]. The unique properties of BL20B2 are high spatial coherence (large coherent length) and its wide beam cross-section, which come from its long beam transport path and bending magnet light source. The horizontal angular aperture of BL20B2 is 1.5 mrad, as in all bending magnet beamlines at SPring-8. The horizontal beam width at the end station is larger than 300 mm for a 215 m beamline length.     

Unexpected effect of catalyst concentration on photochemical CO2 reduction by trans(Cl)–Ru(bpy)(CO)2Cl2: new mechanistic insight into the CO/HCOO– selectivity

Photochemical CO₂ reduction catalysed by trans(Cl)–Ru(bpy)(CO)₂Cl₂ (bpy = 2,2′-bipyridine) efficiently produces carbon monoxide (CO) and formate (HCOO^–) in N,N-dimethylacetamide (DMA)/water containing [Ru(bpy)₃]²⁺ as a photosensitizer and 1-benzyl-1,4-dihydronicotinamide (BNAH) as an electron donor. We have unexpectedly found catalyst concentration dependence of the product ratio (CO/HCOO^–) in the photochemical CO₂ reduction: the ratio of CO/HCOO^– decreases with increasing catalyst concentration. The result has led us to propose a new mechanism in which HCOO^– is selectively produced by the formation of a Ru(i)–Ru(i) dimer as the catalyst intermediate. This reaction mechanism predicts that the Ru–Ru bond dissociates in the reaction of the dimer with CO₂, and that the insufficient electron supply to the catalyst results in the dominant formation of HCOO^–. The proposed mechanism is supported by the result that the time-course profiles of CO and HCOO^– in the photochemical CO₂ reduction catalysed by [Ru(bpy)(CO)₂Cl]₂ (0.05 mM) are very similar to those of the reduction catalysed by trans(Cl)–Ru(bpy)(CO)₂Cl₂ (0.10 mM), and that HCOO^– formation becomes dominant under low-intensity light. The kinetic analyses based on the proposed mechanism could excellently reproduce the unusual catalyst concentration effect on the product ratio. The catalyst concentration effect observed in the photochemical CO₂ reduction using [Ru(4dmbpy)₃]²⁺ (4dmbpy = 4,4′-dimethyl-2,2′-bipyridine) instead of [Ru(bpy)₃]²⁺ as the photosensitizer is also explained with the kinetic analyses, reflecting the smaller quenching rate constant of excited [Ru(4dmbpy)₃]²⁺ by BNAH than that of excited [Ru(bpy)₃]²⁺. We have further synthesized trans(Cl)–Ru(6Mes-bpy)(CO)₂Cl₂ (6Mes-bpy = 6,6′-dimesityl-2,2′-bipyridine), which bears bulky substituents at the 6,6′-positions in the 2,2′-bipyridyl ligand, so that the ruthenium complex cannot form the dimer due to the steric hindrance. We have found that this ruthenium complex selectively produces CO, which strongly supports the catalytic mechanism proposed in this work.     

The relationship between the drug concentration profiles in plasma and the drug doses in the colon

After the dosing of an extended-release (ER) formulation, compounds may exist in solutions at various concentrations in the colon because the drugs are released at various speeds from the ER dosage form. The aim of this study was to investigate the relationship between the drug concentration profiles in plasma and the drug doses in the colon. Several drug solutions of different concentrations were directly administered into the ascending colon of dogs using a lubricated endoscope, and the effects of the drug dose on colonic absorption were estimated. As a result, dose-dependency of colonic absorption varied from compound to compound. Although the relative bioavailability of colonic administration of diclofenac, metformin and cevimeline compared to oral administration was similar regardless of the drug doses in the colon, colonic absorption of diltiazem varied according to the doses. From the results of the co-administration of verapamil and fexofenadine, it was clear that diltiazem underwent extensive hepatic and gastrointestinal first-pass metabolism, resulting in a low area under the curves (AUC) at a low drug dose. During the design of oral ER delivery systems, a colonic absorption study of candidate compounds should be carried out at several solutions of different drug concentrations and assessed carefully.