Multifunctional coupling agents for living cationic polymerization. I. Sodiomalonate anions for vinyl ethers

A series of multifunctional malonate anions, [Na^⊕?C(COOEt)₂CH₂]_mC₆H_6?m(I; m = 2–4), were examined as polymer coupling agents for the living cationic polymerization of vinyl ethers initiated with the hydrogen iodide/zinc iodide (HI/ZnI₂) initiating system. The bifunctional anion ( 2 ;I, m = 2), 1,4-[Na^⊕?C(COOEt)₂CH₂]₂C₆H₄, terminated living polymers of isobutyl vinyl ether (IBVE) (DP _n = 10) almost quantitatively in toluene at ?15°C to give coupled living polymers with doubled molecular weights in 96% yield; the dianion 2 was dissolved in tetrahydrofuran containing 18-crown-6 for maintaining the solution homogeneous. The yield of the coupled polymers was increased with shorter living chains or in less polar solvents. Also by coupling via 2 , ABA block copolymers were obtained from living AB block polymers of IBVE and an ester-functionalized vinyl ether (CH₂?CHOCH₂CH₂OCOCH₃). Coupling of living poly(IBVE) with the trifunctional anion ( 3 ; I, m = 3) led to tri-armed polymers in 56% yield, whereas with the tetrafunctional version ( 4 ; I, m = 4), only three out of the four anions reacted to give another tri-armed polymer in 85% yield. © 1993 John Wiley & Sons, Inc.     

Bottom-up and top-down approach for periodic microstructures on thin oxide films by controlled photo-activated chemical processes

Micropatterned oxide films were fabricated by controlling the photo-induced processes, such as buckling driven wrinkle formation and photomigration, in the photo monomer-oxide precursor hybrid films. The photo-induced process depended on the wavelength of the illuminated light, that is to say, the penetration depth of the UV light for polymerization; a uniform illumination of 254 nm light from the incoherent black light induces the surface buckling which resulted in the self-organized formation of a long-range ordered surface wrinkle structure (bottom-up process). On the other hand, 325 nm or 365 nm illumination enables us to fabricate a microstructure by the conventional photolithography technique, such as the mask method or holographic illumination (top-down process). The simultaneous illumination of the black light (uniform, 254 nm) and the He–Cd laser (holographic, 325 nm) resulted in the formation of a 2D micropattern in which the holographic gratings are formed by the holographic illumination together with the array of dots by surface buckling. This result indicates that the present microfabrication offers an integration of the top-down and bottom-up approach to realize the simultaneous fabrication of multi-scale and complex microstructured thin oxide films for photonic applications.     

Construction of Pt complex within Zr-based MOF and its application for hydrogen production under visible-light irradiation

The present article deals with Pt complex construction within Zr-based MOF having bipyridine units in the framework (Zr-MOF-bpy-PtCl₂) and its photocatalytic activity for hydrogen production under visible-light irradiation (λ > 420 nm). Zr-MOF-bpy-PtCl₂ is prepared by the construction of a Zr-based MOF using 2,2′-bipyridine-5,5′-dicarboxylic acid (Zr-MOF-bpy), and subsequent complexation reaction with K₂PtCl₄. XRD and N₂ adsorption–desorption measurements have revealed that both Zr-MOF-bpy and Zr-MOF-bpy-PtCl₂ have a UiO-type structure. From the results of UV–Vis and XAFS measurements, the incorporated Pt species has been proven to be in square planar geometry involving two N atoms and two Cl atoms as a result of the Pt coordination with bipyridine units in the framework. Zr-MOF-bpy-PtCl₂ has been employed for a hydrogen production reaction from water containing a sacrificial electron donor under visible-light irradiation (λ > 420 nm). Zr-MOF-bpy-PtCl₂ realizes steady hydrogen production, and the amount of evolved hydrogen reaches 8.3 μmol after the 9 h reaction period, while Zr-MOF-bpy exhibits no photocatalytic activity under the same conditions. It has also been found that the activity of Zr-MOF-bpy-PtCl₂ is superior to that of the corresponding homogeneous complex analogue (bpy)PtCl₂.     

Superacid‐catalyzed Friedel–Crafts phosphination of 2‐hydroxybiphenyls with phosphorus trichloride

Cyclic phosphorus compounds, 6H‐dibenz[c,e][1,2]oxaphosphorin‐6‐oxide derivatives, were efficiently synthesized by the Friedel–Crafts reaction of 2‐hydroxybiphenyls with phosphorus trichloride in the presence of superacids, especially trifluoromethanesulfonic acid (TfOH) as a catalyst. TfOH was investigated for the first time as an effective catalyst for the aromatic phosphination of 2‐hydroxybiphenyls.     

Biogenous iron oxide-immobilized palladium catalyst for the solvent-free Suzuki–Miyaura coupling reaction

Iron oxide produced by iron-oxidizing bacteria, Leptothrix ochracea, (biogenous iron oxide: BIO) was used as a support for immobilized palladium catalysts with organic cross-linkers. Palladium immobilized on BIO bearing imidazolium chloride delivered the desired biaryl products in sufficient yields in the Suzuki–Miyaura coupling reactions under solvent-free conditions and could be reused several times without significant loss of catalytic activity. It is shown that BIO can be exploited as a useful support for immobilization of palladium and the BIO-immobilized palladium catalyst effectively promotes the solvent-free Suzuki–Miyaura coupling reactions.     

Synthesis of proton conductive inorganic–organic hybrid membranes from organoalkoxysilane and hydroxyalkylphosphonic acid

Proton conductive inorganic–organic hybrid membranes were synthesized from 3-glycidyloxypropyltrimethoxysiane (GPTMS), phenyltriethoxysilane (PhTES) and hydroxyalkylphosphonic acid. Two kinds of hydroxyalkylphosphonic acids, 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) and hydroxyethanephosphonic acid (HEPA), were incorporated into the membranes as functional molecules for proton conduction. FT-IR and Raman studies revealed the presence of phosphonic acid groups in the hybrid membranes. ¹³C and ²⁹Si NMR confirmed that a three-dimensional siloxane network was formed in the prepared hybrid membrane by hydrolysis and condensation reactions. DTA-TG analysis showed that these membranes were thermally stable up to 200 °C. The HEDPA-based system was found to have higher proton conductivities than the HEPA-based one. The proton conductivities of the hybrid membranes increased with the phosphonic acid content and temperature up to 130 °C. The conductivities of the HEDPA/GPTMS/PhTES membranes = 1/1.6/0.4 were 1.0 × 10⁻¹ and 4.5 × 10⁻⁴ S cm⁻¹ at 100% relative humidity and non-humidified conditions, respectively, at 130 °C.     

Kationische Polymerisation von Styrolen mit Protonsäuren und deren Derivaten. 2. Mitt. Zwei Wachstums-Spezies bei der Polymerisation mit CF3SO3H

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