Macromolecular synthesis using mesoporous zeolites

Mesoporous zeolites such as MCM‐41 were found to serve as nano‐flasks for free radical polymerization of methyl methacrylate (MMA), where the formation of long‐lived propagating radicals was observed. Al‐MCM‐41 with a Lewis‐acidic aluminosilicate framework catalyzed living ring‐opening polymerization of cyclic esters such as δ‐valerolactone and ϵ‐caprolactone, to give narrow molecular‐weight‐distribution polyesters. With Ti‐MCM‐41, a titanate‐containing mesoporous silica, ring‐opening polymerization of δ‐valerolactone also took place to give a high molecular‐weight polyester. On the other hand, with Ti‐MCM‐41 in the presence of methylaluminoxane (MAO), ethylene was polymerized to give a high molecular‐weight, linear polyethylene.     

Effect of the number of seed polymer particles on the kinetic behavior of the seeded emulsion copolymerization of styrene and acrylamide

The seeded emulsion copolymerizations of styrene and acrylamide were carried out at 50°C using polystyrene latex particles as the seed and potassium persulfate as the initiator, respectively. It was found that the change in the number of seed particles initially charged causes a drastic change in the kinetic behavior of this seeded emulsion copolymerization system: when the number of seed particles initially charged was less than a certain critical value, both styrene and acrylamide started polymerization from the beginning of the reaction. However, when the number of seed particles was higher than this critical value, an apparent induction period suddenly emerged only for acrylamide polymerization, that is, acrylamide did not start polymerization until the styrene conversion exceeded around 75%, while the styrene polymerization started and continued very smoothly from the beginning of the reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2689–2695, 1997     

Improved stability of molecular organic EL devices

Influence of emission sites on emission efficiency and running durability of molecular organic electroluminescent devices was investigated. When fluorescent dye rubrene was doped into TPD diamine hole transport layer, rubrene molecule emitted bright yellow light with a max. luminance of 61 000 cd/m². The device had the highest efficiency of 9.8 Im/W at 100 cd/m². Half-decay time of the device from initial luminance of 530 cd/m² under constant direct current was 3 600 h. On the other hand, when rubrene was doped into BeBq₂ complex electron transport layer, the efficiency was 4.4 Im/W and the half-decay time was 110 h. Thus doping site is found to exert significant influence both on the emission efficiency and the running durability.     

Unusual Disordered Crystal Structure of a Racemate Exhibiting a Novel Enantiomeric Resolution: Preferential Enrichment

Simple recrystallization of racemic (±)-NC leads to preferential enrichment of one enantiomer in the mother liquor, which allows the efficient resolution of the two enantiomers. In the unique disordered crystal structure of the racemate, the two enantiomers form centrosymmetric dimers as the major component.     

In situ and ex situ studies on thermal decomposition process of hydromagnesite Mg5(CO3)4(OH)2·4H2O

Journal of Thermal Analysis and Calorimetry - We investigated crystal structure and the local structure changes during the thermal decomposition of hydromagnesite by using in situ high-temperature...     

Signal-source estimation from magnetic field image obtained using atomic magnetometer and digital micro-mirror device

Optical Review - Visualization of an electromagnetic field distribution is helpful for spatial evaluation of field leakage and can aid in solving inverse problems of signal-source estimation....     

Short synthesis of epi-cytoxazone via oxazoline formation through intramolecular benzylic substitution of a bis-trichloroacetimidate

A short and efficient method for synthesizing epi-cytoxazone via the corresponding oxazoline intermediate was developed. The formation of the oxazoline ring, which proceeds through an S_N1 mechanism to ensure that the trans-oxazoline stereochemistry is retained, was induced by intramolecular benzylic substitution of a 1,2-bis-trichloroacetimidate, starting from the known enantiomerically pure diol.     

Structural and Molecular Basis of the Catalytic Mechanism of Geranyl Pyrophosphate C6-Methyltransferase: Creation of an Unprecedented Farnesyl Pyrophosphate C6-Methyltransferase

Prenyl pyrophosphate methyltransferases enhance the structural diversity of terpenoids. However, the molecular basis of their catalytic mechanisms is poorly understood. In this study, using multiple strategies, we characterized a geranyl pyrophosphate (GPP) C6-methyltransferase, BezA. Biochemical analysis revealed that BezA requires Mg²⁺ and solely methylates GPP. The crystal structures of BezA and its complex with S-adenosyl homocysteine were solved at 2.10 and 2.56 Å, respectively. Further analyses using site-directed mutagenesis, molecular docking, molecular dynamics simulations, and quantum mechanics/molecular mechanics calculations revealed the molecular basis of the methylation reaction. Importantly, the function of E170 as a catalytic base to complete the methylation reaction was established. We also succeeded in switching the substrate specificity by introducing a W210A substitution, resulting in an unprecedented farnesyl pyrophosphate C6-methyltransferase.     

Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption

The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al₂O₃) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al₂O₃ nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al₂O₃ multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al₂O₃ nanosheets possess high surface areas up to 425 and 371 m² g⁻¹, respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al₂O₃ multilayered nanosheets exhibit Mo adsorption capacities of 33.1–40.8 mg g⁻¹. The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.     

A practical method for heterogeneously-catalyzed Mizoroki–Heck reaction: Flow system with adjustment of microwave resonance as an energy source

The microwave-assisted and continuous-flow Mizoroki–Heck reaction using a heterogeneous palladium catalyst supported on the anion-exchange resin DIAION WA30 (7% Pd/WA30) is described. The microwave resonance is finely adjusted to 2.4?GHz according to the electric permittivity of the reaction medium for efficient heating. Organic solvents, such as acetonitrile, N,N-dimethylacetamide, and toluene, can be sufficiently heated even with a low intensity of microwave irradiation in a 7% Pd/WA30-packed, glass tube-shaped catalyst cartridge, which was designed based on the electric permittivity of the solvents. The catalyst cartridge can be continuously reused at least 5 runs without exchange.