Syntheses,Structures, and Reactivities of Two Chalcogen‐Stabilized Carbones

Electronic effects on the central carbon atom of carbone, generated by the replacement of the S^IV ligand of carbodisulfane (CDS) with other chalcogen ligands (Ph₂E, E=S or Se), were investigated. The carbones Ph₂E→C←SPh₂(NMe) [E=S( 1 ) or Se( 2 )] were synthesized from the corresponding salts, and their molecular structures and electronic properties were characterized. The carbone 2 is the first carbone containing selenium as the coordinated atom. DFT calculations revealed the electronic structures of 1 and 2 , which have two lone pairs of electrons at the carbon center. The trend in HOMO energy levels, estimated by cyclic voltammetry measurements, for the carbones and CDS follows the order of 2 > 1 >CDS. Analysis of a doubly protonated dication and trication complex revealed that the central carbon atom of 2 behaves as a four‐electron donor.     

Direct patterning of poly(amic acid) and low‐temperature imidization using a crosslinker,a photoacid generator,and a thermobase generator

A positive‐type photosensitive polyimide (PSPI) based on poly(amic acid) (PAA), a crosslinker 1,1,1‐tris{4‐[2‐(vinyloxy)ethoxy]phenyl}ethane (TVPE), a photoacid generator (PAG) (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐2‐(methylphenyl)acetonitrile (PTMA), and a thermobase generator (TBG) t‐butyl 2,6‐dimethylpiperidine‐1‐carboxylate (BDPC) has been developed as a promising material in microelectronics. The PAA was prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐oxydianiline (ODA) in dimethyl sulfoxide (DMSO). The PSPI, consisting of PAA (69 wt %), TPVE (21 wt %), PTMA (3 wt %), and BDPC (7 wt %), showed high sensitivity of 21 mJ/cm² and a high contrast of 6.8 when it was exposed to a 436‐nm line (g‐line), postbaked at 90 °C for 5 min, and developed with 1.69 wt % TMAHaq. A clear positive image of 8 μm line and space pattern was printed on film, which was exposed to 50 mJ/cm² of g‐line by a contact printing mode and fully converted to the corresponding polyimide (PI) pattern on heating at 200 °C, confirmed by FTIR spectroscopy. Thus, this system will be a good candidate for next generation PSPIs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3362–3369, 2009     

Kinetic and equilibrium studies of urea adsorption onto activated carbon: Adsorption mechanism

We found that activated carbon effectively removed urea from solution and that urea adsorption onto activated carbon followed a pseudo-second-order kinetic model. We classified the urea adsorption on activated carbon as physical adsorption and found that it was best described by the Halsey adsorption isotherm, suggesting that the multilayer adsorption of urea molecules on the adsorption sites of activated carbon best characterized the adsorption system. The mechanism of adsorption of urea by activated carbon involved two steps. First, an amino (–NH₂) group of urea interacted with a carbonyl (–C?O) group and a hydroxyl (?OH) group on the surface of activated carbon via dipole–dipole interactions. Next, the –C?O group of the urea molecule adsorbed to the activated carbon interacted with another –NH₂ group from a second urea molecule, leading to multilayer adsorption.     

Pattern formation of polyimide by using photosensitive polybenzoxazole as a top layer

A versatile method for positive-type patterning of polyimide (PI) based on a two-layer photosensitive poly(benzoxazole) (PSPBO) and poly(amic acid) (PAA) film has been developed to provide a promising material in the field of microelectronics. This patterning system consisted of a pristine PAA thick bottom-layer and a poly(o-hydroxy amide) (PHA) thin top layer with 9,9-bis[4-(tert-butoxycarbonyl-methyloxy)phenyl]fluorene (TBMPF) as a dissolution inhibitor, and (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)-acetonitrile (PTMA) as a photoacid generator (PAG). The PHA and PAA were prepared from 4,4′-(hexafluoroisopropylidene)-bis(o-aminophenol) and 4,4′-oxybis(benzoic acid) derivatives, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline, respectively, in N,N-dimethylacetamide. This two-layer system based on PHA (150-nm thickness) and PAA (1.5-μm thickness) showed high sensitivity of 35 mJ/cm² and high contrast of 10.3 when exposed to a 365 nm line (i-line), post-baked at 100 °C for 2 min, and developed in a 2.38 wt.% tetramethylammonium hydroxide aqueous solution/5 wt.% iso-propanol at 25 °C. A clear positive image of a 4-μm line-and-space pattern was printed on a film which was exposed to 100 mJ/cm² of i-line by a contact-printing mode and fully converted to the corresponding PBO/PI pattern upon heating at 350 °C, confirmed by FT-IR spectroscopy. This two-layer system could be applied to the patterning of various PAAs.     

Development of ion transportation, extraction and neutralization systems for atomic beam resonance method

A device that produces a low-energy and largely spin polarized RI beam based on the atomic beam resonance method (RIABR) has been developed. We have performed measurements of stopping and drifting an incoming RI ion beam in a gas chamber, extraction of the ions into a vacuum region, and neutralization of the extracted low-energy ion beam. The drift efficiency of RI ions in a gas and the extraction efficiency at a Laval-type glass nozzle were found to be 0.72±0.04 and 0.033, respectively. The result of the experiment for the neutralization is also discussed.     

Effect of Sn and Nb on generalized stacking fault energy surfaces in zirconium and gamma hydride habit planes

We have investigated the effects of Sn and Nb on dislocation properties in a Zr lattice to elucidate the role of these alloying elements in hydride nucleation processes. According to experimental observations, γ-hydride habit planes are close to the prismatic plane in pure Zr and close to the basal plane in Zircaloy. Dislocation loops are observed around hydride precipitates, implying they play a part in hydride formation. Our ab initio generalized stacking-fault energy calculations showed remarkable effects of Sn on unstable-stacking energy and stacking-fault energy: these parameters for basal slip were considerably reduced while those for prismatic slip were increased in the presence of Sn. These results suggest selective stabilization and enhancement of dislocation spreading in the basal plane, promoting possible elementary processes of hydride precipitation with basal habit plane, i.e. screw-dislocation spreading and edge-dislocation emission in the basal plane.     

A Structurally Robust Chiral Borate Ion: Molecular Design,Synthesis, and Asymmetric Catalysis

Catalysis by chiral weakly‐coordinating anions (WCAs) remains underdeveloped due to the lack of a molecular design strategy for exploiting their characteristics, such as the non‐nucleophilic nature. Here, we report the development of a chiral borate ion comprising an O,N,N,O‐tetradentate backbone, which ensures hitherto unattainable structural robustness. Upon pairing with a proton, the hydrogen borate acts as an effective catalyst for the asymmetric Prins‐type cyclization of vinyl ethers, providing access to structurally and stereochemically defined dihydropyrans. The key to selectivity control is the distinct ability of the borate ion to discriminate the prochiral faces of the acyclic oxonium ion intermediate and dictate the regiochemical outcome. We anticipate that this study paves the way for exploring the untapped potential of WCA catalysis for selective chemical synthesis.