Thermostable poly(p-phenylene sulfide sulfonic acid) as ion exchangers

Poly(p-phenylene sulfide sulfonic acid) was thermally crosslinked for use as a cation exchange polymer with high thermal stability. The decomposition temperature (T_d) of the polymer increases with an increase in the crosslinking temperature. The crosslinking reaction at 300°C in air resulted in the formation of a strongly acidic cation exchange polymer with a T = 467°C and having an SO₂ bond, whose crosslinked structure was investigated using IR spectroscopy.     

Regio- and stereoisomeric control of the aggregation of zinc-chlorins possessing inverted interactive hydroxyl and carbonyl groups.

As models for a self-aggregative, naturally occurring magnesium-chlorin bacteriochlorophyll-d possessing 3(1)-secondary alcoholic hydroxyl and 13(1)-oxo groups, zinc-chlorins were synthesized with 3(1)-oxo and 13(1)-secondary (1) or tertiary hydroxyl groups (2). Compared to the monomers in a tetrahydrofuran solution, diastereomers 13(1)R-1R and 13(1)S-1S gave red-shifted absorption maxima (643 --> 674 nm in 1R and 708 nm in 1S) in 1 v/v% CH(2)Cl(2)-hexane solution, indicating their self-aggregation. Therefore, the positioning of the two groups at 3(1)/13(1) or 13(1)/3(1) on the N21-N23 molecular (Q(y)) axis is not necessarily important for the self-aggregation. The (1)H NMR and CD spectroscopic studies showed that the 674 nm absorbing species of 1R was characterized as a face-to-face "closed" dimer, while the 708 nm absorbing species of 1S was a large oligomer constructed with aggregation of head-to-tail "open" dimers. This diastereomeric control over the aggregation of 1R and 1S is more pronounced than that observed in the regioisomerically 3(1)-secondary alcoholic R/S-diastereomers 3R and 3S. The difference is ascribable to the conformational fixation of the 13(1)-hydroxyl group of the exo five-membered ring in 1. In contrast to self-aggregative 3(1)-tertiary alcoholic 4, both 13(1)-epimers of 13(1)-tertiary alcoholic 2 were monomeric even in nonpolar organic media: the additional 13(1)-methyl group (1 --> 2) drastically suppressed the self-aggregation due to the interference of the methyl group in intermolecular pi-pi interaction.     

Gas diffusion electrodes for polymer electrolyte fuel cell using sulfonated polyimide

Gas diffusion electrodes for high temperature polymer electrolyte fuel cells (PEFCs) have been prepared by using a novel proton conductive sulfonated polyimide (SPI) electrolyte. The catalyst layer was composed of Pt-loaded carbon black (Pt-CB) and SPI ionomer. The polarization properties and the microstructure of the catalyst layer were investigated as a function of the SPI/CB weight ratio. The anodic polarization was found to be negligibly small for all the compositions examined. The highest cathode performance was obtained at SPI/CB = 0.5 (by weight), where the best balance of high catalyst utilization and oxygen gas diffusion rate through the ionomer was obtained.     

Ab initio fragment molecular orbital (FMO) method applied to analysis of the ligand-protein interaction in a pheromone-binding protein

Full quantum computation of the electronic state of proteins has recently become possible by the advent of the ab initio fragment molecular orbital (FMO) method. We applied this method to the analysis of the interaction between the Bombyx mori pheromone-binding protein and its ligand, bombykol. The protein–ligand interaction of this molecular complex was minutely analyzed by the FMO method, and the analysis revealed several important interactions between the ligand and amino acid residues.     

Synthesis,Characterization, and Catalytic Activity of a Cubic [Mo3S4Pd] Cluster Bearing Bulky Cyclopentadienyl Ligands

A cubic metal-sulfur cluster containing three Mo ions and a Pd ion, [Cp^SiEt3₃Mo₃S₄Pd]Cl ( Mo₃Pd , Cp^SiEt3=C₅Me₄SiEt₃), was synthesized by the incorporation of the Pd ion into a Mo₃S₄ cluster [Cp^SiEt3₃Mo₃S₄] ( Mo₃ ). Mo₃Pd was characterized by ¹H NMR, UV-vis, X-ray crystallography, and cyclic voltammetry measurements. The electrochemical measurements demonstrated reversible one- and two-electron reduction processes for Mo₃Pd , which suggested potential catalytic activity for two-electron substrate reductions such as hydrogen evolution reaction. Controlled potential electrolysis in the presence of Mo₃Pd and trifluoroethanol in THF solvent displayed H₂ formation with a constant current over 60 min. The amount of generated H₂ by Mo₃Pd was two times higher than Mo₃ , indicating the catalytic activity facilitated by the Pd center. The mechanism of the catalytic cycle was determined by density functional theory.     

The decay of the Tz = −12 nuclide 59Zn

The decay of ⁵⁹Zn was studied with an isotope separator on-line. From the β- and γ-rays the half-life and E^max(β⁺) of ⁵⁹Zn were found to be 183.7 ± 2.3 ms and 8100 ± 100 keV, respectively, and the ft-value and the GT matrix element were deduced. Delayed protons in the decay of ⁵⁹Zn were also studied.     

Freezing-out of nuclear polarization in radioactive core ions of microclusters, “snowballs” in superfluid helium

A novel method was tried successfully to trap ions and to freeze out their nuclear polarization inside aggregates of helium atoms, snowballs, in superfluid helium. Spin polarized¹²B (T _1/2=20.4 ms) ions were introduced into superfluid helium and snowballs were created around the impinged impurity ions. Beta-ray asymmetry was measured to obtain the nuclear polarization of decaying¹²B. The comparison with the initial value of¹²B polarization produces that no relaxation in polarization was observed throughout lifetime of¹²B.     

Radical/Iminium Domino Strategy (RIDS) for Rapid Construction of Sterically Congested γ-Lactam-Based Multiheterocycles

Cu-Catalyzed radical/iminium domino strategy (RIDS) for the efficient synthesis of quaternary-carbon-containing γ-lactam-based multiheterocyclic structures from α-bromocarboxamides is reported. This domino reaction strategy enables the construction of multiheterocycles in one step. Mechanistic studies showed that two catalytically generated iminiums are likely to be key intermediates in the catalytic cycle. The developed method can be used in a chemoselective manner to produce multicyclic products in the reaction with ketones possessing two different carbonyls.     

Anion conductive aromatic polymers containing fluorenyl groups: Effect of the position and number of ammonium groups

Synthesis and properties of anion conductive aromatic block copolymers, QPE‐bl‐3, QPE‐bl‐3 M2, and M4, containing fluorenylidene biphenylene groups as scaffold for ammonium groups are described. These copolymers share the same main chain structure, but the position and the number of ammonium groups on a fluorenyl group differ. High molecular weight quaternized block copolymers were obtained via typical chloromethylation reaction or using preaminated monomers, and were well‐characterized by ¹H NMR spectra. Self‐standing bendable membranes were obtained by solution casting. QPE‐bl‐3 M4 membranes containing four ammonium groups per hydrophilic repeat unit (highest ammonium density) in the hydrophilic block exhibited well developed phase‐separated morphology, while QPE‐bl‐3 membranes containing two ammonium groups per hydrophilic repeat unit exhibited high anion conductivity. The highest anion conductivity (104 mS/cm) was obtained with QPE‐bl‐3 membrane (IEC = 2.1 meq/g) at 80 °C in water. An H₂/O₂ alkaline fuel cell was operable with the membrane to achieve 62 mW/cm² of the maximum power density at 161 mA/cm² of the current density. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 935–944     

New poly(arylene ether)s with pendant phosphonic acid groups

Soluble brominated poly(arylene ether)s containing mono‐ or dibromotetraphenylphenylene ether and octafluorobiphenylene units were synthesized. The polymers were high molecular weight (weight‐average molecular weight = 115,100–191,300; number‐average molecular weight = 32,300–34,000) and had high glass‐transition temperatures (>279 °C) and decomposition temperatures (>472 °C). The brominated polymers were phosphonated with diethylphosphite by a palladium‐catalyzed reaction. Quantitative phosphonation was possible when 50 mol % of a catalyst based on bromine was used. The diethylphosphonated polymers were dealkylated by a reaction with bromotrimethylsilane in carbon tetrachloride followed by hydrolysis with hydrochloric acid. The polymers with pendant phosphonic acid groups were soluble in polar solvents such as dimethyl sulfoxide and gave flexible and tough films via casting from solution. The polymers were hygroscopic and swelled in water. They did not decompose at temperatures of up to 260 °C under a nitrogen atmosphere. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3770–3779, 2001