Polymerization of phenylacetylene by WCl6·Ph4Sn: Synthesis of high polymer achieved by selection of solvents

Phenylacetylene was polymerized by WCl₆·Ph₄Sn (1:1) in 1,4-dioxane to provide in high yield a polymer whose molecular weight reached 1 × 10⁵. The polymerization also proceeded in other oxygen-containing solvents (ethers, esters, and ketones) but the polymer molecular weights were lower than 1 × 10⁴. Certain hydrocarbon solvents such as cyclohexene, tetralin, and indan also afforded high-molecular-weight polyphenylacetylene [M _n = (5–8) × 10⁴], as compared with those (M _n ≤ 1.5 × 10⁴) obtained in conventional aromatic hydrocarbons like benzene. A high polymer (M _n = 1.6 × 10⁵) was also formed from β-naphthylacetylene in 1,4-dioxane. It was inferred that the active hydrogens of these solvents prevent the formed polymer from being decomposed by a radical mechanism and/or modify the nature of active species.     

Preparation of micron-size monodisperse polymer microspheres having cationic groups

Micron-size monodisperse crosslinked polymer microspheres having chloromethyl groups were prepared by seeded copolymerization of styrene, divinylbenzene, and chloromethylstyrene in the presence of 2.1- monodisperse polystyrene seed particles produced by dispersion polymerization. The modification reaction of chloromethyl groups on the surfaces with polyamines such as triethylenetetramine and ethylenediamine was carried out. From the measurements of potential and the amount of chloride ion released, the introduction of a large number of cationic groups at the surfaces was confirmed.Part CXXXI of the series Studies on suspension and Emulsion.     

Features and mechanism of H- anion emission from 12 CaO x 7 Al2O3 surface

The hydrogen anion (H-) and other anionic species (O-, OH-, e-) in the gas phase, emitted from the synthesized crystal surface of 12 CaO x 7 Al2O3-H- (C12A7-H-), have been observed. The emission intensity of all the anionic species strongly depends on the sample surface temperature and the extraction field. H- has the highest emission branch ratio, and the extraction field can reduce its apparent activation energy. H- emission current at a microA/cm2-level has been achieved, which is about 4 orders of magnitude higher than that obtained from the thermal desorption process of CaH2. The observed anions of H- and OH- are attributed to their migration from the C12A7-H- cages onto the surface [i.e., Y-(cages) --> Y-(surface) --> Y-(gas phase) (Y = H, OH)]. The weak O- and electron emission would both arise from the dissociation of O2-: O2-(surface) --> O-(surface) + e-(surface) --> O-(gas phase) + e-(space).     

Investigation of Drug Nanoparticle Formation by Co-grinding with Cyclodextrins: Studies for Indomethacin, Furosemide and Naproxen

Drugs with poor water solubility were co-ground with cyclodextrins (CDs) to create nanoparticles with improved solubility characteristics. Indomethacin (IDM), furosemide (FRM) and naproxen (NAP) were co-ground with β-CD at the molar ratio of 2:1 (CD:drug). Co-grinding of a drug with CD resulted in not only the formation of drug nanoparticles but also the solubilization of the drug by inclusion complex formation with CD in aqueous media. The nanoparticle fraction of IDM, and FRM from ground mixtures prepared with β-CD was as high as 60–70% while the solubilization fraction was less than 10%. In contrast, β-CD–NAP ground mixture showed a large fraction, 48%, for drug solubilization and only 4% for nanoparticle formation. Furosemide ground mixtures prepared with α-CD, β-CD and γ-CD showed comparatively high nanoparticle fraction while the solubilization fraction was around 10%. Both the nanoparticle fraction and the solubilization fraction were greater in the IDM–β-CD system than those in γ-CD and α-CD systems. The nanoparticle formation of NAP depended on the types of CD used as a co-grinding additive. Naproxen nanoparticles could be prepared by co-grinding NAP and α-CD, while the solubilization of NAP tended to improve when β-CD or γ-CD was used.     

Biodegradation of Eu(III)-citrate complexes by Pseudomonas fluorescens

Summary We have investigated the structure of Eu(III)-citrate complexes in aqueous solution and their degradability by Pseudomonas fluorescens. Analysis of 1:1, 1:2, and 1:5 Eu(III):citrate solutions at pH 7 by electrospray ionization mass spectrometry (ESI-MS) showed that the 2:2 Eu(III)-citrate complex is the predominant complex species at a low citrate/Eu(III) ratio, while at a high ratio, a 1:2 Eu(III)-citrate complex is formed preferably. Studies on the biodegradation of Eu(III)-citrate complex by P. fluorescens have shown that a 2:2 Eu(III)-citrate complex is resistent to degradation while a 1:2 complex transforms to a 2:2 complex with the degradation of excess citric acid.     

Synthesis of enzymatically crosslinkable peptide-poly(L-lysine) conjugate and creation of bio-inspired hybrid fibers

Poly(L-lysine)s having an Nepsilon-substituted tetrapeptide, Lys-Gly-Tyr-Gly, were synthesized by the coupling of the protected tetrapeptide active ester, Boc-Lys(Z)-Gly-Tyr(Bzl)-Gly (4-hydroxyphenyl)dimethylsulfonium methylsulfate and Nepsilon-group of the poly(L-lysine) side chain. The Nepsilon-substituted tetrapeptide functions as the substrate of tyrosinase and is responsible for the enzyme-mediated interpolymer cross-linking. The degree of Nepsilon-substitution (DS) was mostly controlled by changing the stoichiometry between the Nepsilon-amino groups of the parent poly(L-lysine) and the protected tetrapeptide active ester. Two kinds of samples having DS values of 8.6 and 18 mol-% were prepared. The resulting cationic Nepsilon-(Lys-Gly-Tyr-Gly)-poly(L-lysine) (abbreviated as PLL(GYGK)) was spun into hybrid fibers with the anionic polysaccharide gellan via a polyionic complexation reaction at the interface between aqueous solutions of the two polymers. The mechanical strengths of the PLL(GYGK)-gellan hybrid fibers were superior to those of the original poly(L-lysine)-gellan fibers. The mechanical strength of the hybrid fibers further increased upon the tyrosinase-mediated cross-linking reaction of the PLL(GYGK). This result indicates that the covalent cross-bridge formation between the Nepsilon-substituted peptides significantly contributed to reinforcement of the hybrid fibers. The present study affords a new methodology for reinforcement inspired by a biological process.     

The 4s electron densities of Fe impurity atoms in some transition and noble metals

From internal conversion experiments and the Mössbauer effect measurements, the 4s electron density and isomer shift for Fe impurity atoms in Cr, Ni, Cu, Pt and Au metals were studied. The M and N shell conversion electron spectra of the 14.4 keV transition of⁵⁷Fe were measured using a high resolution β-ray spectrometer and analyzed using a deconvolution methods. The Mössbauer effect measurements were performed by a standard spectrometer with a moving absorber. Most of the samples showed isomer shift values consistent with the published ones. It is concluded that the 4s electron density, \(\rho _{4_S} (0)\) , at the nucleus of⁵⁷Fe embedded is nearly equal in these host metals. The relation between \(\rho _{4_S} (0)\) and the isomer shift indicates that \(\rho _{3_S} (0)\) plays an important role in the variation of the isomer shift.     

On the outradius of the teichmüller space

Let Γ be a fuchsian group which preserves the unit disc Δ and hence also its complement Δ^* in the Riemann sphere . The Bers embedding represents the Teichm=:uller space T(Γ) of Γ in the space (B (Δ^*, Γ) of bounded quadratic differentials for Γ in Δ^*. Then, T(Γ) is included in the closed ball centred at the origin of radius 6 inB(Δ^*, Γ) with respect to the norm employed in a paper by Nehari [The Schwarzian derivative and Schlicht functions; Bull. Amer. Math. Soc. 55 (1949), 545–551]. In other words the outradiuso(Γ) ofT(Γ) is not greater than 6. The purpose of this paper is to give a complete characterization of a fuchsian group Γ for which the outradiuso(Γ) ofT(Γ) attains this extremal value 6. The main theorem is: Let Γ be a fuchsian group preserving Δ^*. Then the outradiuso(Γ) of the Teichmüller spaceT(Γ) equals 6 if and only if for any positive numberd, either (i) there exists a hyperbolic disc of radiusd precisely invariant under the trivial subgroup, or (ii) there exists the collar of widthd about the axis of a hyperbolic element of Γ. Dedicated to Professor K?taro Oikawa on his 60th birthday     

Conformation of 2-aminomethylpyrrolidine and 2-aminomethylpiperidine in ternary platinum(II) complexes: regulation of conformation of the diamine by the coexisting ligand

Square-planar complexes with the formula [Pt(L(2))(L(1))](X)(2) x nH(2)O, where L(1) is S-2-aminomethylpyrrolidine (S-pyrda) or 2-aminomethylpiperidine (pipda) and L(2) is diammine (X=Cl), cyclobutane-1,1-dicarboxylato (cbdca) (X=none), 2,2'-bipyridine (bpy) (X=NO(3)), or 1,10-phenanthroline (phen) (X=Cl), were prepared and the nature of the coordination of L(1) was examined by (1)H-NMR spectroscopy and X-ray crystallography. These 2-aminomethylazacycloalkane derivatives form five-membered chelate rings condensed with an azacycloalkane ring in cis- or trans-configurations. The (1)H-NMR spectrum of complexes with S-pyrda as L(1) were consistent with cis-condensed rings in an S(N) conformation with any of L(2) group. However, (1)H-NMR spectra of the complexes with pipda as L(1) indicated trans-fused successive rings for the diammine and cbdca as L(2), but spectra for bpy and phen as L(2) were consistent with a conformation having cis-fused successive rings. X-Ray crystallography data for the two complexes with pipda as L(1) and cbdca (1) and bpy (2) as L(2) confirms the different coordination behavior in the solid state.