Structure and properties of polybutylene crystallized from the glassy state. II. Electron microscopy

Electron microscope studies of as-ultraquenched and subsequently crystallized isotactic polybutylene (PB) are described in this paper. Cold shadowing of the as-quenched samples reveals no distinct structure larger than 30 Å in the amorphous PB. When rapidly warmed to room temperature PB crystallizes as microcrystals of size ranging from 100 to 250 Å. The size of the microcrystals can be changed only by annealing at temperatures higher than T_α; in PB this resulted in the growth of short lamellae. However, by warming the quenched samples slowly to room temperature, large morphological units were obtained. The effect of several quenchants on the crystallization process of PB is also discussed.     

L12 phase formation and giant exchange anisotropy in Mn3Ir/Co–Fe bilayers

The degree of order S of Mn–Ir layers and the exchange anisotropy of Mn–Ir/Co–Fe bilayers were investigated for various chemical compositions of Mn–Ir layers, underlayer materials, and underlayer thicknesses. It was found that: (1) The compositional range over which L1₂-phase Mn₃Ir could be formed is 22–32 at% Ir and giant exchange anisotropy is obtained in this range. (2) Ru is favorable as an underlayer material for avoiding interdiffusion with the Mn–Ir layer during deposition on the temperature elevated substrate. (3) The underlayer thickness could be reduced to 5 nm while maintaining a giant exchange anisotropy in excess of 1 erg/cm².     

Tunable magnetic anisotropy of antiferromagnetic superlattice and resultant exchange bias of ferromagnetic layer on it

Exchange biasing of ferromagnetic layer deposited on the antiferromagnetic superlattice was investigated in (Co₇₀Fe₃₀/Ru)_29.5/Ru/Co₉₀Fe₁₀ multilayers. Uniaxial magnetic anisotropy (K_AF) was induced and tuned in the antiferromagentic superlattice by uniaxial substrate bending method through the inverse effect of magnetostriction. The exchange bias increased and tended to be saturated with increasing the K_AF, while it was not observed at K_AF=0.     

fac‐Tris(2‐ethyl‐4‐oxo‐4H‐pyran‐3‐olato‐κ2O3,O4)­iron(III) and its aluminium(III) analog

The crystal structures of the title iron(III) and aluminium(III) ethyl maltolate complexes, [Fe(C₇H₇O₃)₃] and [Al(C₇H₇O₃)₃], respectively, are isomorphous. In each case, the three bidentate ligand mol­ecules are bound to the metal atom, forming a distorted octahedral coordination geometry in a fac configuration.     

Living polymerization of ethylphenylketene by samarium enolate

The living polymerization of ethylphenylketene (EPK) by a samarium enolate is described. Poly(EPK) with controlled molecular weight and low polydispersity was obtained in a quantitative yield by the polymerization with the samarium enolate and polar additives. A wide variety of polar additives including amides and ureas were shown to facilitate the formation of well‐defined poly(EPK).     

Phenanthrene adsorption from solution on single wall carbon nanotubes

Phenanthrene was adsorbed from ethanol solution to the surface of single wall carbon nanotubes, which were previously physically and chemically characterized. Different anionic surfactants were added in the solutions to enhance the phenanthrene solubility and apparently have also improved the dispersion of two respective nanotube samples used. Adsorbed amount was determined through the concentration difference measured by UV-visible spectrophotometry. Results suggest that adsorption of phenanthrene is extremely improved in the case of nanotube purified with higher quality. These findings were confirmed by X-ray photoelectron spectroscopy. The influence of the surfactant on the adsorption kinetics of phenanthrene is suggested to be significant as well.     

Coumarin-strapped calix[4]pyrrole: a fluorogenic anion receptor modulated by cation and anion binding

A new strapped calix[4]pyrrole containing a fluorophore as part of the strap has been synthesized and characterized. Association constants with various anions have been determined using both fluorescence titration and isothermal titrations calorimetry (ITC). The two sets of association constants were found to be in good agreement with one another. The fluorescence emission properties of this new receptor could be controlled by addition of Na+ (or H2O) and anions. However, the fluorescence quenching by anions is only observed in the presence of Na+ (or H2O). All the experimental evidence is consistent with the notion that independent PET processes are modulated by separate cation and anion recognition events. As such, this system operates as an elementary logic gate wherein anion and cation concentrations serve as the input and fluorescence intensity changes provide the output.     

Cis- and trans-strapped calix[4]pyrroles bearing phthalamide linkers: synthesis and anion-binding properties

[reaction: see text] New cis-strapped calix[4]pyrrole derivatives 12, 13, and 19 and trans-strapped systems 14 and 15 bearing isophthalate-derived diamide spacers linked to the tetrapyrrolic core have been synthesized and characterized by spectroscopic means. The anion-binding behavior of these receptors was investigated by proton NMR spectroscopy and isothermal titration calorimetry (ITC). A 2:1 binding stoichiometry was observed under the conditions of NMR analysis but not at the lower concentration regime used for ITC. As gauged from both sets of analyses, these new strapped systems display affinities for halide anions that are enhanced compared to those of normal, unstrapped calix[4]pyrrole. However, contrary to expectations, no size-dependent selectivity for anions is observed as the length of the bridging strap is varied. Such results are interpreted in terms of anion-binding processes that occur outside the central pocket defined by the strap but that still favor strong associations as the result of the increased number of hydrogen-bonding donors the amide groups provide.     

Threading-followed-by-shrinking protocol for the synthesis of a [2]rotaxane incorporating a Pd(II)-salophen moiety

This communication describes a new protocol for the construction of [2]rotaxanes: "threading-followed-by-shrinking". This approach involves the threading of a rodlike unit through a crown ether-like macrocycle and then shrinking the size of the macrocycle's cavity through coordination of a transition-metal ion by a salophen moiety in the macrocycle. The self-assembly of the macrocycle and a thread, followed by addition of palladium acetate, afforded the [2]rotaxane, which contains a palladium(II)-salophen moiety, after counterion exchange. This [2]rotaxane was characterized fully by NMR and IR spectroscopic, mass spectrometric, and elemental and X-ray crystallographic analyses.