Effective photochemical synthesis of an air-stable anthracene-based organic semiconductor from its diketone precursor

A diketone precursor of air-stable bis-2-thienyl-2,6-anthracene was prepared and quantitatively converted to the target acene by photoirradiation of the n-π^∗ absorption both in solution and as a film, in air.     

Preparation of Molecule‐Responsive Microsized Hydrogels via Photopolymerization for Smart Microchannel Microvalves

Microdevices designed for practical environmental pollution monitoring need to detect specific pollutants such as dioxins. Bisphenol A (BPA) has been widely used as a monomer for the synthesis of polycarbonate and epoxy resins. However, the recent discovery of its high potential ability to disrupt human endocrine systems has made the development of smart systems and microdevices for its detection and removal necessary. Molecule‐responsive microsized hydrogels with β‐cycrodextrin (β‐CD) as ligands are prepared by photopolymerization using a fluorescence microscope. The molecule‐responsive micro‐hydrogels show ultra‐quick shrinkage in response to target BPA. Furthermore, the flow rate of a microchannel is autonomously regulated by the molecule‐responsive shrinking of their hydrogels as smart microvalves.

     

Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques

There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next‐generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X‐ray absorption fine structure) method and by a quick‐XAFS(QXAFS) method. Information on the site‐preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro‐crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation.     

Well‐Defined Iron Complexes as Efficient Catalysts for “Green” Atom‐Transfer Radical Polymerization of Styrene,Methyl Methacrylate,and Butyl Acrylate with Low Catalyst Loadings and Catalyst Recycling

Environmentally friendly iron(II) catalysts for atom‐transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N‐trialkylated‐1,4,9‐triazacyclononane (R₃TACN) ligands. Two types of structures were confirmed by crystallography: “[(R₃TACN)FeX₂]” complexes with relatively small R groups have ionic and dinuclear structures including a [(R₃TACN)Fe(μ‐X)₃Fe(R₃TACN)]⁺ moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R₃TACN)FeX₂]_n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)₃TACN}FeBr₂] ( 4 b ) was the best catalyst for the well‐controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.     

Organic Dicarboxylate Negative Electrode Materials with Remarkably Small Strain for High‐Voltage Bipolar Batteries

As advanced negative electrodes for powerful and useful high‐voltage bipolar batteries, an intercalated metal–organic framework (iMOF), 2,6‐naphthalene dicarboxylate dilithium, is described which has an organic‐inorganic layered structure of π‐stacked naphthalene and tetrahedral LiO₄ units. The material shows a reversible two‐electron‐transfer Li intercalation at a flat potential of 0.8 V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33 %. The material possesses two‐dimensional pathways for efficient electron and Li⁺ transport formed by Li‐doped naphthalene packing and tetrahedral LiO₃C network. A cell with a high potential operating LiNi_0.5Mn_1.5O₄ spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96 % capacity retention after 100 cycles), high specific energy (300 Wh kg^?1), and high specific power (5 kW kg^?1). An 8 V bipolar cell was also constructed by connecting only two cells in series.     

Volumetric study on the inclusion complex formation of α- and β-cyclodextrin with 1-alkanols at different temperatures

The partial molar volumes (V_a) of 1-alkanols (carbon number, m=5, 6, 7) in - and -cyclodextrin (CD) solutions at 5.00 mmol kg^–1 have been determined as a function of alkanol concentration (C_a) between 293.2 and 308.2 K by using a dilatometer. It has been observed that with an increase in C_a, V_a increased in -CD solution but decreased in -CD solution, asymptotically to a value of V_a in CD-free water. The dependence of V_a on C_a provided the binding constant (K) of 1:1 complex, the volume change in complex formation, and the partial molar volume of complex itself. The complex formation mechanism has been discussed on the basis of these values and their carbon number dependences in the respect of geometric behavior, hydrophobic interaction, and van der Waals interaction. It is concluded that the CD cavity in water is not rigid but flexible for fitting in nicely with guest molecule.     

Reliability tests for Weibull distribution with variational shape parameter based on sudden death lifetime data

In the traditional design of reliability tests for assuring the mean time to failure (MTTF) in Weibull distribution with shape and scale parameters, it has been assumed that the shape parameter in the acceptable and rejectable populations is the same fixed number. For the purpose of expanding applicability of the reliability testing, Hisada and Arizono have developed a reliability sampling scheme for assuring MTTF in the Weibull distribution under the conditions that shape parameters in the both populations do not necessarily coincide, and are specified as interval values, respectively. Then, their reliability test is designed using the complete lifetime data. In general, the reliability testing based on the complete lifetime data requires the long testing time. As a consequence, the testing cost becomes sometimes expensive. In this paper, for the purpose of an economical plan of the reliability test, we consider the sudden death procedure for assuring MTTF in Weibull distribution with variational shape parameter.