Polymerizable Tautomers. VII. Radical Copolymerization of Ethyl 3-oxo-4-Pentenoate and Ethyl 4-Methyl-3-oxo-4-Pentenoate with Methyl Methacrylate

Abstract

Ethyl 3-oxo-4-pentenoate (EAA) and ethyl 4-methyl-3-oxo-4-pentenoate (EMAA) exhibit the coexistence of the ketonic and enolic forms in most organic solvents. Radical copolymerizations of EAA and EMAA with methyl methacrylate (MMA) were carried out at 60 °C in various solvents, and monomer reactivity ratios were estimated. There are minor solvent effects on monomer reactivity ratios r_MMA in both EAA/MAA and EM A A/MM A systems. On the other hand, r_EAA and r_MMA values greatly change with the solvent: The values decrease with an increase in the ketonic fraction of the polymerizable tautomers (EAA and EMAA). Regression analysis of the monomer reactivity ratios with the solvatochromic parameters reveals that polarity of the solvent is the major factor governing the relative reactivity.     

In-beam Mössbauer study of 57Fe using a secondary 57Mn beam and ion implantation

We have succeeded in obtaining well-resolved M?ssbauer spectra of ⁵⁷Fe arising from short-lived ⁵⁷Mn ( T _1/2 = 1.45 min) in Si and KMnO₄. The M?ssbauer spectra of ⁵⁷Fe in Si are well fitted with a curve consisting of two singlet lines, one being assigned as the interstitial Fe atoms and the other as substitutional ones. The relative intensities of the two lines infer that 60% of ⁵⁷Fe ( ←⁵⁷Mn) atoms land at the interstitial sites and 40% at the substitutional sites at temperatures between 30 K and 296 K. The result for the KMnO₄ sample suggests a presence of an exotic chemical species corresponding to a higher valence state than Fe^{6 +}. Received: 1 May 2001 / Accepted: 4 December 2001     

Electrochemical formation of intermediate layer for Co/Pd multilayered media

Pd nanocluster seeds were formed on a soft magnetic underlayer (SUL) using an electrochemical substitution reaction, and were utilized as an intermediate layer for a Co/Pd multilayered ([Co/Pd]_n) perpendicular magnetic recording medium. A CoNiFeB film prepared with electroless deposition was used as SUL, which was immersed into a PdCl₂ solution for the formation of Pd seeds. The Pd seeds were found to effectively reduce the size of magnetic domains in the [Co/Pd]_n film deposited on them. The optimization of the concentration of the PdCl₂ solution and the use of the pretreatment process with a SnCl₂ solution were effective to obtain the smooth SUL surface with fine Pd seeds as small as 5 nm. The 20 nm-thick [Co/Pd]_n film deposited on the optimized Pd seeds/CoNiFeB SUL exhibited a high coercivity of 7.8 kOe and a small magnetic domain size of 69 nm. These results indicated that the combination of the Pd seeds and the electroless-deposited SUL was desirable in terms of the improvement not only in the magnetic properties of [Co/Pd]_n media but also in the mass productivity of the underlayer.     

Production of spin-polarized 17N beam using inverse-kinematics low-energy transfer reactions

A new method to produce spin-polarized radioactive nuclear beams has been developed, which takes advantage of the low-energy transfer reaction in inverse kinematics. The method provides beam energies of a convenient range so that they may be implanted in a thin stopper, yet allowing the stopper to be spatially separated from the production target. The presence of polarizations of sizes at least $\left|P\right|\sim 0.5 \%$ has been confirmed for a ¹⁷N beam obtained from ⁹Be(¹⁸O,¹⁷N) reaction at $\theta_{\rm Lab} \sim -1.7\,^{\circ}$ .     

Enantioselective fluorination mediated by cinchona alkaloid derivatives/Selectfluor combinations: reaction scope and structural information for N-fluorocinchona alkaloids.

Cinchona-alkaloid/Selectfluor combinations efficiently fluorinate a variety of carbonyl compounds in a highly enantioselective manner to furnish chiral alpha-fluorocarbonyl compounds. The DHQB/Selectfluor combination is effective for the enantioselective fluorination of indanones and tetralones 1 in up to 91% ee. The first enantioselective syntheses of chiral derivatizing reagents 3 was accomplished with high ee and in high chemical yields by the DHQDA/Selectfluor combination. 3-Fluorooxindoles 7 were prepared with ee up to 83% using the (DHQ)2AQN/Selectfluor or the (DHQD)2PYR/Selectfluor combination. Since the combinations are conveniently prepared in situ from readily available reagents, the present system represents a practical method for enantioselective fluorination. X-ray crystallography and 1H NMR analyses of the cinchona alkaloids/Selectfluor combination have established that the species that mediate this novel reaction are N-fluoroammonium cinchona alkaloid tetrafluoroborates, which adopt open conformations.     

Heat dissipation and magnetic properties of surface-coated Fe3O4 nanoparticles for biomedical applications

In this study, the influence of surface coating on the magnetic and heat dissipation properties of Fe₃O₄ nanoparticles was investigated. Fe₃O₄ nanoparticles that ranged in size between (particle sizes of 20 and 30 nm) were coated with polyethylenimine (PEI), oleic acid, and Pluronic F-127. Surface coatings that were composed of thick layers of oleic acid and Pluronic F-127 reduced dipole interactions between the particles, and resulted in reduced coercivity and decreased Néel relaxation times. The ac magnetization measurements revealed that the heat dissipation of the PEI-coated Fe₃O₄ nanoparticles was induced by hysteresis loss and Brownian relaxation loss and that of the oleic-acid-coated Fe₃O₄ nanoparticles was mainly induced by hysteresis loss and Néel relaxation loss.     

Local tunneling barrier height observations of NiAl(1 1 0)

Local work functions at individual atoms on a compound metal surface have been experimentally examined. The simultaneously obtained STM and local tunneling barrier height (LBH) images of NiAl(1 1 0) show that LBH at geometrically lower Ni sites is much higher than that at geometrically higher Al sites, indicating that each individual atom on the NiAl(1 1 0) surface has a specific potential barrier for relevant electrons.     

Fabrication of fluorescent nanoparticles of dendronized perylenediimide by laser ablation in water

Highly fluorescent organic nanoparticles with size of about 300 nm were prepared by nanosecond laser ablation of micrometer-sized powder of dendronized perylenediimide dispersed in water. The nanoparticle colloidal solution provided a fluorescence quantum yield of 0.58. The absorption and emission spectral studies demonstrated that the bulky dendron groups at the side bays of perylenediimide chromophore efficiently suppress the interchromophoric interactions in the nanoparticles. Fluorescence measurement on several single nanoparticles underlines that the prepared nanoparticles are bright and photo-stable enough to be a useful probe for single particle fluorescence investigation.